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How to: Grant and revoke control of a shared resource

Learn how to use Microsoft Lync 2013 SDK to grant and revoke control of a locally shared resource in a Lync 2013 conversation.

The topic in this section builds on the sample application introduced in What you can do with desktop, application, and display sharing and continued in How to: Get a shareable resource and share it in a conversation. Figure 1 highlights the part of the sample Windows Form discussed in this topic.

The tasks in the following list are discussed in this topic and shown in the code samples. For an overview of resource sharing in Lync 2013, see Sharing resources in a conversation.

  • Verifying that you can grant control of a locally shared resource to another user.

  • Granting control of a locally shared resource to another user.

  • Verifying that you can revoke control of a locally shared resource to another user.

  • Revoking control of a locally shared resource.

Figure 1. Grant and revoke control buttons

Grant and revoke control buttons

The prerequisites for granting and revoking control of a locally shared resource are as follows:

  • Microsoft Lync 2013 must be installed and running on the development computer.

  • You must have sign-in credentials for Microsoft Lync Server 2013.

  • Microsoft Lync 2013 SDK must be installed on the development computer.

Core concepts to know

Understanding the following concepts is essential to using resource sharing conversions in an application.

Topic

Description

Sharing resources in a conversation

Learn about programmatically sharing a computer monitor, desktop, or running program with another Lync 2013 user in a conversation window by using classes in Microsoft Lync 2013 SDK.

Application sharing modality

Learn about the ApplicationSharingModality class and how it enables you to share resources in an application.

Before your application runs the logic in this topic, a resource sharing conversation must be active with one or more participants in addition to the local user. The local user participation state must be Microsoft.Lync.Model.Conversation.Sharing.ParticipationState.Sharing and a local sharable resource must be shared in the conversation. For information about reaching this starting application state, see How to: Get a shareable resource and share it in a conversation.

You can only grant control of a resource that is shared locally and not controlled by another conversation participant. To simplify your code, track the availability of control actions on the Modality.ActionAvailabilityChanged event for all the Microsoft.Lync.Model.Conversation.Sharing.ApplicationSharingModality objects in a conversation. For information about handling this event, see How to: Get a shareable resource and share it in a conversation.

Note Note

The participant who is sharing a local resource has the participation state of Microsoft.Lync.Model.Conversation.Sharing.ParticipationState.Sharing. All other participants have the participation state of Microsoft.Lync.Model.Conversation.Sharing.ParticipationState.Viewing unless they are requesting control of the shared resource. In this case, they are Sharing.ParticipationState.RequestingControl. When the sharing participant accepts a control request, the requesting participant is ParticipationState.Controlling.

There can be only one ParticipationState.Sharing participant at a time. There can be zero or one ParticipationState.Controlling participant at a time. There can be many ParticipationState.RequestingControl participants.

If there is no Microsoft.Lync.Model.Conversation.Sharing.ParticipationState.Controlling participant, the resource is shared but not controlled.

Call the BeginGrantControl method

Call the ApplicationSharingModality.BeginGrantControl method on the application sharing modality of the conversation participant that is being granted control of the locally shared resource.

ApplicationSharingModality events

Two events are raised on the Conversation Microsoft.Lync.Model.Conversation.Sharing.ApplicationSharingModality object when control of a resource has been granted. The Modality.ActionAvailabilityChanged event is raised twice to indicate that the Grant action is no longer available but the Revoke action is now available. The ApplicationSharingModality.ControllerChanged event is raised to indicate that there is now a resource controller and provides a Microsoft.Lync.Model.Contact object that represents the new controller.

ParticipationStateChanged events

When the control granting operation is finished, the participant who is granted control is now a ParticipationState.Controlling participant. The controlling participant is notified of this state change in the ApplicationSharingModality.ParticipationStateChanged event. The participation state of the sharing participant does not change.

If the sharing participant revokes control of the shared resource, the controlling participant becomes a viewing participant and the ApplicationSharingModality.ParticipationStateChanged event is raised on that participant’s application sharing modality.

Code example

The following example completes the following steps.

  1. Obtains the SIP URI of the selected conversation participant from the UI list of participants.

  2. Obtains a Microsoft.Lync.Model.Conversation.Sharing.ApplicationSharingModality object from a Dictionary<string,Microsoft.Lync.Model.Conversation.Sharing.ApplicationSharingModality>.

    The dictionary contains references to the application sharing modality objects of all participants. For a listing of the sample code that declares and fills this dictionary, see How to: Start a resource sharing conversation.

  3. Verifies that control of the shared resource can be granted and then grants control to the selected participant.

         /// <summary>
        ///Grant another participant control of a locally owned and shared resource.
        ///The Grant button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is
        ///called with the event argument that specifies the ModalityAction.GrantSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Grant_Button_Click(object sender, EventArgs e)
        {
            if (Contact_ListBox.SelectedItems.Count == 0)
            {
                return;
            }
            //Get the sharing modality of the participant which the local user has selected to control the locally owned resource.
            try
            {
                //_particpantSharingModalities is a class field of type Dictionary<string, ApplicationSharingModality>.
                //It is filled in the Conversation.ParticipantAdded event callback method of this sample.
                ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[Contact_ListBox.SelectedItem.ToString()];
 
                //If the application sharing modality is available and the resource can still be granted then grant
                //control of the resource.
                if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.GrantSharingControl))
                {
                    sharingModality.BeginGrantControl(SharingControlCallback, "grant");
                }
            }
            catch (NullReferenceException) { MessageBox.Show("Chosen participant does not have an application sharing modality.""Grant control error"); }
 
        }

The following example is invoked by the platform thread on completion of the asynchronous ApplicationSharingModality.BeginGrantControl.

        /// <summary>
        /// Callback method for all asynchronous modality control methods.
        /// </summary>
        /// <param name="ar"></param>
        private void SharingControlCallback(System.IAsyncResult ar)
        {
            //Get the application sharing modality for the conversation participant to invoke controlling action on.
            ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[_ResourceControllingContact.Uri];
 
            //Complete the asynchronous controlling action according to the asynchronous state string that indicates
            //which controlling action to complete.
            switch (ar.AsyncState.ToString().ToUpper())
            {
                case "ACCEPT":
                    sharingModality.EndAcceptControlRequest(ar);
                    break;
                case "DECLINE":
                    sharingModality.EndDeclineControlRequest(ar);
                    break;
                case "GRANT":
                    sharingModality.EndGrantControl(ar);
                    break;
                case "RELEASE":
                    sharingModality.EndReleaseControl(ar);
                    break;
                case "REQUEST":
                    sharingModality.EndRequestControl(ar);
                    break;
                case "REVOKE":
                    sharingModality.EndRevokeControl(ar);
                    break;
                case "DISCONNECT":
                    sharingModality.EndDisconnect(ar);
                    break;
            }
        }

The following example handles the event raised when a conversation participant is granted control of the locally shared resource. It is important that you maintain a reference to the participant who is controlling a resource.

When revoking control of the resource, you must call the ApplicationSharingModality.BeginRevokeControl method on the ApplicationSharingModality of that participant.

        /// <summary>
        /// Handles the event raised when the participant that is controlling the shared conversation application resource
        /// changes. This event is raised locally even when the shared resource is not locally owned.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ControllerChanged(object sender, ControllerChangedEventArgs e)
        {
            this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { ResourceControllerName_Label, e.ControllerName });
 
            //Store the Contact object for the conversation participant that now controls the shared conversation resource.
            _ResourceControllingContact = ((ApplicationSharingModality)sender).Controller.Contact;
 
        }

You can only revoke control of a resource that is owned and shared locally. Control of the resource must have been previously granted to another conversation participant. Call the ApplicationSharingModality.BeginRevokeControl method on the ApplicationSharingModality of the participant who is controlling the resource.

Tip Tip

When your application accepts a control request of another user, control is automatically revoked from the current controlling user. You do not need to call the ApplicationSharingModality.BeginRevokeControl method before accepting the new control request.

ApplicationSharingModality events

When control of the locally shared resource is revoked, the Grant action is available and the Revoke action is no longer available. Two Modality.ActionAvailabilityChanged events are raised. The first event shows the ModalityActionAvailabilityChangedEventArgs.Action property value of ModalityAction.GrantSharingControl is available. The second event shows the ModalityActionAvailabilityChangedEventArgs.Action property value of ModalityAction.RevokeSharingControl is not available.

Code example

The following example revokes control of a locally owned and share resource that is controlled by a resource viewer. The _ResourceControllingContact object is a class field of type Microsoft.Lync.Model.Contact. It is filled in the previous example when the control of the resource changes as a result of a grant operation.

        /// <summary>
        ///Revoke control of a remotely controlled resource and locally owned shared resource.
        ///The Revoke button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is called
        ///with the event argument that specifies the ModalityAction.RevokeSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Revoke_Button_Click(object sender, EventArgs e)
        {
            if (_ResourceControllingContact == null)
            {
                return;
            }
            ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[_ResourceControllingContact.Uri];
            if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.RevokeSharingControl))
            {
                sharingModality.BeginRevokeControl(SharingControlCallback, "revoke");
            }
 
        }

When your application has granted and revoked a locally shared resource, the resource is shown on the content stage of all participants with no participants in control. In addition, the ModalityAction.GrantSharingControl action is available. You can now grant sharing control of the locally shared resource to another participant. The participants who are viewing the shared resource can request control of the resource. For information about accepting or declining a request to control a resource, see How to: Accept or decline a request to control a shared resource.

The following example declares the Windows form that is shown in figure 1. The resource sharing sample is a complete solution that uses all of the methods, events, and properties of the application sharing modality to give a user all of the sharing features exposed by the modality.

namespace ShareResources
{
    partial class ShareResources_Form
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.ClientState_Label = new System.Windows.Forms.Label();
            this.ClientStateString_Label = new System.Windows.Forms.Label();
            this.Contact_ListBox = new System.Windows.Forms.ListBox();
            this.StartSharingResource_Button = new System.Windows.Forms.Button();
            this.Accept_Button = new System.Windows.Forms.Button();
            this.Decline_Button = new System.Windows.Forms.Button();
            this.Grant_Button = new System.Windows.Forms.Button();
            this.SharingAction_GroupBox = new System.Windows.Forms.GroupBox();
            this.Disconnect_Button = new System.Windows.Forms.Button();
            this.Revoke_Button = new System.Windows.Forms.Button();
            this.Request_Button = new System.Windows.Forms.Button();
            this.Release_Button = new System.Windows.Forms.Button();
            this.SharingParticipationState_Label = new System.Windows.Forms.Label();
            this.SharingParticipationStateString_Label = new System.Windows.Forms.Label();
            this.SharedResources_ListBox = new System.Windows.Forms.ListBox();
            this.ConversationActions_Group = new System.Windows.Forms.GroupBox();
            this.EndConversation_Button = new System.Windows.Forms.Button();
            this.Start_Button = new System.Windows.Forms.Button();
            this.ResourceController_Label = new System.Windows.Forms.Label();
            this.ResourceControllerName_Label = new System.Windows.Forms.Label();
            this.ShareableResources_Label = new System.Windows.Forms.Label();
            this.ContactList_Label = new System.Windows.Forms.Label();
            this.SharedResource_Label = new System.Windows.Forms.Label();
            this.groupBox1 = new System.Windows.Forms.GroupBox();
            this.Acceptx_Button = new System.Windows.Forms.Button();
            this.RejectX_Button = new System.Windows.Forms.Button();
            this.RefreshResource_Button = new System.Windows.Forms.Button();
            this.SharingAction_GroupBox.SuspendLayout();
            this.ConversationActions_Group.SuspendLayout();
            this.groupBox1.SuspendLayout();
            this.SuspendLayout();
            // 
            // ClientState_Label
            // 
            this.ClientState_Label.AutoSize = true;
            this.ClientState_Label.Location = new System.Drawing.Point(13, 13);
            this.ClientState_Label.Name = "ClientState_Label";
            this.ClientState_Label.Size = new System.Drawing.Size(64, 13);
            this.ClientState_Label.TabIndex = 0;
            this.ClientState_Label.Text = "Client State:";
            // 
            // ClientStateString_Label
            // 
            this.ClientStateString_Label.AutoSize = true;
            this.ClientStateString_Label.Location = new System.Drawing.Point(112, 15);
            this.ClientStateString_Label.Name = "ClientStateString_Label";
            this.ClientStateString_Label.Size = new System.Drawing.Size(58, 13);
            this.ClientStateString_Label.TabIndex = 1;
            this.ClientStateString_Label.Text = "Signed out";
            // 
            // Contact_ListBox
            // 
            this.Contact_ListBox.FormattingEnabled = true;
            this.Contact_ListBox.Location = new System.Drawing.Point(13, 63);
            this.Contact_ListBox.Name = "Contact_ListBox";
            this.Contact_ListBox.SelectionMode = System.Windows.Forms.SelectionMode.MultiSimple;
            this.Contact_ListBox.Size = new System.Drawing.Size(180, 82);
            this.Contact_ListBox.TabIndex = 2;
            // 
            // StartSharingResource_Button
            // 
            this.StartSharingResource_Button.Location = new System.Drawing.Point(12, 397);
            this.StartSharingResource_Button.Name = "StartSharingResource_Button";
            this.StartSharingResource_Button.Size = new System.Drawing.Size(153, 23);
            this.StartSharingResource_Button.TabIndex = 3;
            this.StartSharingResource_Button.Text = "4) Share Resource";
            this.StartSharingResource_Button.UseVisualStyleBackColor = true;
            this.StartSharingResource_Button.Click += new System.EventHandler(this.StartSharingResource_Button_Click);
            // 
            // Accept_Button
            // 
            this.Accept_Button.Enabled = false;
            this.Accept_Button.Location = new System.Drawing.Point(11, 28);
            this.Accept_Button.Name = "Accept_Button";
            this.Accept_Button.Size = new System.Drawing.Size(130, 23);
            this.Accept_Button.TabIndex = 4;
            this.Accept_Button.Text = "Accept";
            this.Accept_Button.UseVisualStyleBackColor = true;
            this.Accept_Button.Click += new System.EventHandler(this.Accept_Button_Click);
            // 
            // Decline_Button
            // 
            this.Decline_Button.Enabled = false;
            this.Decline_Button.Location = new System.Drawing.Point(11, 57);
            this.Decline_Button.Name = "Decline_Button";
            this.Decline_Button.Size = new System.Drawing.Size(130, 23);
            this.Decline_Button.TabIndex = 5;
            this.Decline_Button.Text = "Decline";
            this.Decline_Button.UseVisualStyleBackColor = true;
            this.Decline_Button.Click += new System.EventHandler(this.Decline_Button_Click);
            // 
            // Grant_Button
            // 
            this.Grant_Button.Enabled = false;
            this.Grant_Button.Location = new System.Drawing.Point(11, 86);
            this.Grant_Button.Name = "Grant_Button";
            this.Grant_Button.Size = new System.Drawing.Size(130, 23);
            this.Grant_Button.TabIndex = 6;
            this.Grant_Button.Text = "Grant";
            this.Grant_Button.UseVisualStyleBackColor = true;
            this.Grant_Button.Click += new System.EventHandler(this.Grant_Button_Click);
            // 
            // SharingAction_GroupBox
            // 
            this.SharingAction_GroupBox.Controls.Add(this.Disconnect_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Revoke_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Request_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Release_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Accept_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Grant_Button);
            this.SharingAction_GroupBox.Controls.Add(this.Decline_Button);
            this.SharingAction_GroupBox.Location = new System.Drawing.Point(235, 15);
            this.SharingAction_GroupBox.Name = "SharingAction_GroupBox";
            this.SharingAction_GroupBox.Size = new System.Drawing.Size(162, 232);
            this.SharingAction_GroupBox.TabIndex = 7;
            this.SharingAction_GroupBox.TabStop = false;
            this.SharingAction_GroupBox.Text = "6) Take a control action";
            // 
            // Disconnect_Button
            // 
            this.Disconnect_Button.Enabled = false;
            this.Disconnect_Button.Location = new System.Drawing.Point(11, 202);
            this.Disconnect_Button.Name = "Disconnect_Button";
            this.Disconnect_Button.Size = new System.Drawing.Size(130, 23);
            this.Disconnect_Button.TabIndex = 10;
            this.Disconnect_Button.Text = "Stop Sharing";
            this.Disconnect_Button.UseVisualStyleBackColor = true;
            this.Disconnect_Button.Click += new System.EventHandler(this.Disconnect_Button_Click);
            // 
            // Revoke_Button
            // 
            this.Revoke_Button.Enabled = false;
            this.Revoke_Button.Location = new System.Drawing.Point(11, 115);
            this.Revoke_Button.Name = "Revoke_Button";
            this.Revoke_Button.Size = new System.Drawing.Size(130, 23);
            this.Revoke_Button.TabIndex = 9;
            this.Revoke_Button.Text = "Revoke";
            this.Revoke_Button.UseVisualStyleBackColor = true;
            this.Revoke_Button.Click += new System.EventHandler(this.Revoke_Button_Click);
            // 
            // Request_Button
            // 
            this.Request_Button.Enabled = false;
            this.Request_Button.Location = new System.Drawing.Point(11, 144);
            this.Request_Button.Name = "Request_Button";
            this.Request_Button.Size = new System.Drawing.Size(130, 23);
            this.Request_Button.TabIndex = 8;
            this.Request_Button.Text = "Request";
            this.Request_Button.UseVisualStyleBackColor = true;
            this.Request_Button.Click += new System.EventHandler(this.Request_Button_Click);
            // 
            // Release_Button
            // 
            this.Release_Button.Enabled = false;
            this.Release_Button.Location = new System.Drawing.Point(11, 173);
            this.Release_Button.Name = "Release_Button";
            this.Release_Button.Size = new System.Drawing.Size(130, 23);
            this.Release_Button.TabIndex = 7;
            this.Release_Button.Text = "Release";
            this.Release_Button.UseVisualStyleBackColor = true;
            this.Release_Button.Click += new System.EventHandler(this.Release_Button_Click);
            // 
            // SharingParticipationState_Label
            // 
            this.SharingParticipationState_Label.AutoSize = true;
            this.SharingParticipationState_Label.Location = new System.Drawing.Point(240, 253);
            this.SharingParticipationState_Label.Name = "SharingParticipationState_Label";
            this.SharingParticipationState_Label.Size = new System.Drawing.Size(27, 13);
            this.SharingParticipationState_Label.TabIndex = 8;
            this.SharingParticipationState_Label.Text = "I am";
            // 
            // SharingParticipationStateString_Label
            // 
            this.SharingParticipationStateString_Label.AutoSize = true;
            this.SharingParticipationStateString_Label.Location = new System.Drawing.Point(264, 253);
            this.SharingParticipationStateString_Label.Name = "SharingParticipationStateString_Label";
            this.SharingParticipationStateString_Label.Size = new System.Drawing.Size(62, 13);
            this.SharingParticipationStateString_Label.TabIndex = 9;
            this.SharingParticipationStateString_Label.Text = " not sharing";
            // 
            // SharedResources_ListBox
            // 
            this.SharedResources_ListBox.FormattingEnabled = true;
            this.SharedResources_ListBox.HorizontalScrollbar = true;
            this.SharedResources_ListBox.Location = new System.Drawing.Point(12, 283);
            this.SharedResources_ListBox.Name = "SharedResources_ListBox";
            this.SharedResources_ListBox.Size = new System.Drawing.Size(181, 108);
            this.SharedResources_ListBox.TabIndex = 11;
            // 
            // ConversationActions_Group
            // 
            this.ConversationActions_Group.Controls.Add(this.EndConversation_Button);
            this.ConversationActions_Group.Controls.Add(this.Start_Button);
            this.ConversationActions_Group.Location = new System.Drawing.Point(12, 158);
            this.ConversationActions_Group.Name = "ConversationActions_Group";
            this.ConversationActions_Group.Size = new System.Drawing.Size(161, 89);
            this.ConversationActions_Group.TabIndex = 13;
            this.ConversationActions_Group.TabStop = false;
            this.ConversationActions_Group.Text = "2) Start a conversation";
            // 
            // EndConversation_Button
            // 
            this.EndConversation_Button.Enabled = false;
            this.EndConversation_Button.Location = new System.Drawing.Point(16, 50);
            this.EndConversation_Button.Name = "EndConversation_Button";
            this.EndConversation_Button.Size = new System.Drawing.Size(130, 23);
            this.EndConversation_Button.TabIndex = 0;
            this.EndConversation_Button.Text = "End";
            this.EndConversation_Button.UseVisualStyleBackColor = true;
            this.EndConversation_Button.Click += new System.EventHandler(this.EndConversation_Button_Click);
            // 
            // Start_Button
            // 
            this.Start_Button.Enabled = false;
            this.Start_Button.Location = new System.Drawing.Point(16, 21);
            this.Start_Button.Name = "Start_Button";
            this.Start_Button.Size = new System.Drawing.Size(130, 23);
            this.Start_Button.TabIndex = 16;
            this.Start_Button.Text = "Start";
            this.Start_Button.UseVisualStyleBackColor = true;
            this.Start_Button.Click += new System.EventHandler(this.Start_Button_Click);
            // 
            // ResourceController_Label
            // 
            this.ResourceController_Label.AutoSize = true;
            this.ResourceController_Label.Location = new System.Drawing.Point(240, 300);
            this.ResourceController_Label.Name = "ResourceController_Label";
            this.ResourceController_Label.Size = new System.Drawing.Size(103, 13);
            this.ResourceController_Label.TabIndex = 14;
            this.ResourceController_Label.Text = "Resource Controller:";
            // 
            // ResourceControllerName_Label
            // 
            this.ResourceControllerName_Label.AutoSize = true;
            this.ResourceControllerName_Label.Location = new System.Drawing.Point(240, 322);
            this.ResourceControllerName_Label.Name = "ResourceControllerName_Label";
            this.ResourceControllerName_Label.Size = new System.Drawing.Size(0, 13);
            this.ResourceControllerName_Label.TabIndex = 15;
            // 
            // ShareableResources_Label
            // 
            this.ShareableResources_Label.AutoSize = true;
            this.ShareableResources_Label.Location = new System.Drawing.Point(13, 267);
            this.ShareableResources_Label.Name = "ShareableResources_Label";
            this.ShareableResources_Label.Size = new System.Drawing.Size(93, 13);
            this.ShareableResources_Label.TabIndex = 17;
            this.ShareableResources_Label.Text = "3) Pick a resource";
            // 
            // ContactList_Label
            // 
            this.ContactList_Label.AutoSize = true;
            this.ContactList_Label.Location = new System.Drawing.Point(12, 44);
            this.ContactList_Label.Name = "ContactList_Label";
            this.ContactList_Label.Size = new System.Drawing.Size(99, 13);
            this.ContactList_Label.TabIndex = 20;
            this.ContactList_Label.Text = "1) Choose contacts";
            // 
            // SharedResource_Label
            // 
            this.SharedResource_Label.AutoSize = true;
            this.SharedResource_Label.Location = new System.Drawing.Point(243, 350);
            this.SharedResource_Label.Name = "SharedResource_Label";
            this.SharedResource_Label.Size = new System.Drawing.Size(33, 13);
            this.SharedResource_Label.TabIndex = 21;
            this.SharedResource_Label.Text = "None";
            // 
            // groupBox1
            // 
            this.groupBox1.Controls.Add(this.RejectX_Button);
            this.groupBox1.Controls.Add(this.Acceptx_Button);
            this.groupBox1.Location = new System.Drawing.Point(235, 381);
            this.groupBox1.Name = "groupBox1";
            this.groupBox1.Size = new System.Drawing.Size(164, 96);
            this.groupBox1.TabIndex = 22;
            this.groupBox1.TabStop = false;
            this.groupBox1.Text = "Sharing Invitiation Action";
            // 
            // Acceptx_Button
            // 
            this.Acceptx_Button.Enabled = false;
            this.Acceptx_Button.Location = new System.Drawing.Point(11, 19);
            this.Acceptx_Button.Name = "Acceptx_Button";
            this.Acceptx_Button.Size = new System.Drawing.Size(130, 23);
            this.Acceptx_Button.TabIndex = 0;
            this.Acceptx_Button.Text = "Accept";
            this.Acceptx_Button.UseVisualStyleBackColor = true;
            this.Acceptx_Button.Click += new System.EventHandler(this.Acceptx_Button_Click);
            // 
            // RejectX_Button
            // 
            this.RejectX_Button.Enabled = false;
            this.RejectX_Button.Location = new System.Drawing.Point(11, 48);
            this.RejectX_Button.Name = "RejectX_Button";
            this.RejectX_Button.Size = new System.Drawing.Size(130, 23);
            this.RejectX_Button.TabIndex = 1;
            this.RejectX_Button.Text = "Reject";
            this.RejectX_Button.UseVisualStyleBackColor = true;
            this.RejectX_Button.Click += new System.EventHandler(this.RejectX_Button_Click);
            // 
            // RefreshResource_Button
            // 
            this.RefreshResource_Button.Location = new System.Drawing.Point(12, 445);
            this.RefreshResource_Button.Name = "RefreshResource_Button";
            this.RefreshResource_Button.Size = new System.Drawing.Size(153, 23);
            this.RefreshResource_Button.TabIndex = 23;
            this.RefreshResource_Button.Text = "Refresh resources";
            this.RefreshResource_Button.UseVisualStyleBackColor = true;
            this.RefreshResource_Button.Click += new System.EventHandler(this.RefreshResource_Button_Click);
            // 
            // ShareResources_Form
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(409, 489);
            this.Controls.Add(this.RefreshResource_Button);
            this.Controls.Add(this.groupBox1);
            this.Controls.Add(this.SharedResource_Label);
            this.Controls.Add(this.ContactList_Label);
            this.Controls.Add(this.ShareableResources_Label);
            this.Controls.Add(this.ResourceControllerName_Label);
            this.Controls.Add(this.ResourceController_Label);
            this.Controls.Add(this.ConversationActions_Group);
            this.Controls.Add(this.SharedResources_ListBox);
            this.Controls.Add(this.SharingParticipationStateString_Label);
            this.Controls.Add(this.SharingParticipationState_Label);
            this.Controls.Add(this.SharingAction_GroupBox);
            this.Controls.Add(this.StartSharingResource_Button);
            this.Controls.Add(this.Contact_ListBox);
            this.Controls.Add(this.ClientStateString_Label);
            this.Controls.Add(this.ClientState_Label);
            this.Name = "ShareResources_Form";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "Share Resources";
            this.Load += new System.EventHandler(this.ShareResources_Form_Load);
            this.SharingAction_GroupBox.ResumeLayout(false);
            this.ConversationActions_Group.ResumeLayout(false);
            this.groupBox1.ResumeLayout(false);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label ClientState_Label;
        private System.Windows.Forms.Label ClientStateString_Label;
        private System.Windows.Forms.ListBox Contact_ListBox;
        private System.Windows.Forms.Button StartSharingResource_Button;
        private System.Windows.Forms.Button Accept_Button;
        private System.Windows.Forms.Button Decline_Button;
        private System.Windows.Forms.Button Grant_Button;
        private System.Windows.Forms.GroupBox SharingAction_GroupBox;
        private System.Windows.Forms.Button Release_Button;
        private System.Windows.Forms.Button Revoke_Button;
        private System.Windows.Forms.Button Request_Button;
        private System.Windows.Forms.Label SharingParticipationState_Label;
        private System.Windows.Forms.Label SharingParticipationStateString_Label;
        private System.Windows.Forms.ListBox SharedResources_ListBox;
        private System.Windows.Forms.GroupBox ConversationActions_Group;
        private System.Windows.Forms.Button EndConversation_Button;
        private System.Windows.Forms.Button Disconnect_Button;
        private System.Windows.Forms.Label ResourceController_Label;
        private System.Windows.Forms.Label ResourceControllerName_Label;
        private System.Windows.Forms.Button Start_Button;
        private System.Windows.Forms.Label ShareableResources_Label;
        private System.Windows.Forms.Label ContactList_Label;
        private System.Windows.Forms.Label SharedResource_Label;
        private System.Windows.Forms.GroupBox groupBox1;
        private System.Windows.Forms.Button RejectX_Button;
        private System.Windows.Forms.Button Acceptx_Button;
        private System.Windows.Forms.Button RefreshResource_Button;
    }
}

The following example interacts with the previously declared Windows Form. The code starts a conversation, chooses a shareable resource, starts the sharing session, and grants and revokes control of the shared resource.

using System;
using System.Windows.Forms;
using Microsoft.Lync.Model;
using Microsoft.Lync.Model.Group;
using Microsoft.Lync.Model.Conversation;
using Microsoft.Lync.Model.Conversation.Sharing;
using System.Collections.Generic;

namespace ShareResources
{
    public partial class ShareResources_Form : Form
    {

        #region class field declarations
        /// <summary>
        /// Lync client platform. The entry point to the API
        /// </summary>
        Microsoft.Lync.Model.LyncClient _LyncClient;

        /// <summary>
        /// Represents a Lync conversation
        /// </summary>
        Conversation _conversation;

        /// <summary>
        /// A Contact instance representing the participant selected to be granted control of a resource
        /// </summary>
        Contact _ResourceControllingContact;

        /// <summary>
        /// Dictionary of all contacts selected from the multi-select enabled contact list on UI
        /// </summary>
        Dictionary<string, Contact> _selectedContacts = new Dictionary<string, Contact>();

        /// <summary>
        /// Collection of all participants application sharing modalities, keyed by Contact.Uri.
        /// See _controllingContact class field...
        /// </summary>
        Dictionary<string, ApplicationSharingModality> _participantSharingModalities = new Dictionary<string, ApplicationSharingModality>();

        /// <summary>
        /// The Application sharing modality of the conversation itself
        /// </summary>
        ApplicationSharingModality _sharingModality;

        /// <summary>
        /// The Application sharing modality of the local participant.
        /// </summary>
        ApplicationSharingModality _LocalParticipantSharingModality;
        #endregion

        #region UI event handlers

        /// <summary>
        /// invoked when sample form is loaded. Initializes fields, gets API entry point, 
        /// registers for events on Lync Client and ConversationManager.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void ShareResources_Form_Load(object sender, EventArgs e)
        {
            try
            {
                //Get the API entry point
                _LyncClient = LyncClient.GetClient();

                //Resource sharing is not supported in UI suppression mode. Sample closes
                //if Lync UI is suppressed
                if (_LyncClient.InSuppressedMode == true)
                {
                    MessageBox.Show("Lync Client is in UI Suppressed mode. Sharing is not supported.", "Application Error", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                    this.Close();
                }

                //Display the current state of the Lync client.
                ClientStateString_Label.Text = _LyncClient.State.ToString();

                //If the Lync client is signed out, sign into the Lync client
                if (_LyncClient.State == ClientState.SignedOut)
                {
                    _LyncClient.EndSignIn(_LyncClient.BeginSignIn(
                        "terrya@contoso.com",
                        "terrya@contoso.com",
                        "MyPassword",
                        null,
                        null));
                }

                //Display the current state of the Lync client.
                ClientStateString_Label.Text = _LyncClient.State.ToString();

                //Register for the three Lync client events needed so that application is notified when:
                // * Lync client signs in or out
                // * A new conversation is added (remotely via invite or locally by user)
                // * A conversation is removed (conversation ends)
                _LyncClient.StateChanged += _LyncClient_StateChanged;
                _LyncClient.ConversationManager.ConversationAdded += ConversationManager_ConversationAdded;
                _LyncClient.ConversationManager.ConversationRemoved += ConversationManager_ConversationRemoved;

                //Enable the start conversation button on the UI
                Start_Button.Enabled = true;

                //ShareDesktop.LoadAllContacts loads the contact list on the UI with  all contacts that are in the user's Lync client contact list.
                LoadAllContacts();

            }
            catch (NotInitializedException)
            {
                MessageBox.Show("Client is not initialized.  Closing form", "Lync Client Error", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                this.Close();
            }
            catch (ClientNotFoundException)
            {
                MessageBox.Show("Client is not running.  Closing form", "Lync Client Error", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                this.Close();
            }
            catch (Exception exc)
            {
                MessageBox.Show("General exception: " + exc.Message, "Lync Client Error", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                this.Close();
            }

        }

        /// <summary>
        /// Handles click event on sharing resource button. User must select a resource
        /// from the sharable resources list before clicking the button.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void StartSharingResource_Button_Click(object sender, EventArgs e)
        {

            //If there is no active conversation to share this resource in, return from handler
            if (_conversation == null)
            {
                return;
            }

            //If there is no sharing modality stored locally on the active conversation, get it from the active conversation and store it.
            if (_sharingModality == null)
            {
                _sharingModality = _conversation.Modalities[ModalityTypes.ApplicationSharing] as ApplicationSharingModality;
            }

            //Process the users selected resource choice by calling this helper method
            ShareSelectedResource(SharedResources_ListBox.SelectedIndex);
        }

       /// <summary>
       ///Accept another participants request to control locally owned and shared resource.
       ///The Accept button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is called
       ///with the event argument that specifies the ModalityAction.AcceptSharingControlRequest action is available.
       /// </summary>
       /// <param name="sender"></param>
       /// <param name="e"></param>
        private void Accept_Button_Click(object sender, EventArgs e)
        {
            Accept_Button.Text = "Accept";

            //_selectedContact is set to the Contact object of the participant who requested control of the resource. 
            //see the _sharingModality_ControlRequestReceived method in the application sharing modality event handlers region.
            ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[_ResourceControllingContact.Uri];

            //If the requesting participant application sharing modality is available and the AcceptSharingControlRequest action can be invoked
            if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.AcceptSharingControlRequest))
            {
                //Accept sharing control request.
                sharingModality.BeginAcceptControlRequest((ar) => {sharingModality.EndAcceptControlRequest(ar);}, null);
            }
        }

        /// <summary>
        ///Decline another participants request to control locally owned and shared resource.
        ///The Decline button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is
        ///called with the event argument that specifies the ModalityAction.DeclineSharingControlRequest action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Decline_Button_Click(object sender, EventArgs e)
        {
            //_selectedContact is set to the Contact object of the participant who requested control of the resource. 
            //see the _sharingModality_ControlRequestReceived method in the application sharing modality event handlers region.
            ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[_ResourceControllingContact.Uri];
            if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.DeclineSharingControlRequest))
            {
                sharingModality.BeginDeclineControlRequest((ar) => { sharingModality.EndDeclineControlRequest(ar); }, null);
            }

        }

        /// <summary>
        ///Grant another participant control of a locally owned and shared resource.
        ///The Grant button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is
        ///called with the event argument that specifies the ModalityAction.GrantSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Grant_Button_Click(object sender, EventArgs e)
        {
            if (Contact_ListBox.SelectedItems.Count == 0)
            {
                MessageBox.Show("Please select a conversation participant");
                return;
            }
            //Get the sharing modality of the participant which the local user has selected to control the locally owned resource.
            try
            {
                ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[Contact_ListBox.SelectedItem.ToString()];

                //If the application sharing modality is available and the resource can still be granted then grant
                //control of the resource.
                if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.GrantSharingControl))
                {
                    sharingModality.BeginGrantControl((ar) => { sharingModality.EndGrantControl(ar); }
                        , null);
                }
            }
            catch (NullReferenceException) { MessageBox.Show("Chosen participant does not have an application sharing modality.", "Grant control error"); }

        }

        /// <summary>
        ///Release control of a remotely owned resource and shared resource.
        ///The Release button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is
        ///called with the event argument that specifies the ModalityAction.ReleaseSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Release_Button_Click(object sender, EventArgs e)
        {
            if (_LocalParticipantSharingModality != null && _LocalParticipantSharingModality.CanInvoke(ModalityAction.ReleaseSharingControl))
            {
                _LocalParticipantSharingModality.BeginReleaseControl((ar) => { _LocalParticipantSharingModality.EndReleaseControl(ar); }, null);
            }
        }

        /// <summary>
        ///Request control of a remotely owned resource and shared resource.
        ///The Request button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is called
        ///with the event argument that specifies the ModalityAction.RequestSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Request_Button_Click(object sender, EventArgs e)
        {
            if (_LocalParticipantSharingModality != null && _LocalParticipantSharingModality.CanInvoke(ModalityAction.RequestSharingControl))
            {
                _LocalParticipantSharingModality.BeginRequestControl((ar) => { _LocalParticipantSharingModality.EndRequestControl(ar); }, null);
            }
        }

        /// <summary>
        ///Revoke control of a remotely controlled resource and locally owned shared resource.
        ///The Revoke button is enabled when the _sharingModality_ActionAvailabilityChanged event handler is called
        ///with the event argument that specifies the ModalityAction.RevokeSharingControl action is available.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Revoke_Button_Click(object sender, EventArgs e)
        {
            if (_ResourceControllingContact == null)
            {
                return;
            }
            ApplicationSharingModality sharingModality = (ApplicationSharingModality)_participantSharingModalities[_ResourceControllingContact.Uri];
            if (sharingModality != null && sharingModality.CanInvoke(ModalityAction.RevokeSharingControl))
            {
                sharingModality.BeginRevokeControl((ar) => 
                {
                    try
                    {

                        sharingModality.EndRevokeControl(ar);
                    }
                    catch (OperationException oe) { MessageBox.Show("Operation exception " + oe.Message); }
                }
                , null);
            }

        }

        private void EndConversation_Button_Click(object sender, EventArgs e)
        {
            if (_conversation == null)
            {
                return;
            }
            if (_conversation.State != ConversationState.Terminated)
            {
                _conversation.End();
            }
        }

        /// <summary>
        /// Starts a new conversation
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Start_Button_Click(object sender, EventArgs e)
        {
            if (_conversation == null)
            {
                Contact aContact;
                foreach (Object selectedObject in Contact_ListBox.SelectedItems)
                {
                    aContact = _LyncClient.ContactManager.GetContactByUri(selectedObject.ToString());
                    if (!_selectedContacts.ContainsKey(selectedObject.ToString()))
                    {
                        _selectedContacts.Add(selectedObject.ToString(), aContact);
                    }
                }
                _conversation = _LyncClient.ConversationManager.AddConversation();
            }

        }

        /// <summary>
        /// Disconnects the conversation application sharing modality so that the user
        /// is no longer sharing or viewing a resource.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Disconnect_Button_Click(object sender, EventArgs e)
        {
            if (_sharingModality != null && _sharingModality.CanInvoke(ModalityAction.Disconnect))
            {
                _sharingModality.BeginDisconnect(ModalityDisconnectReason.None, (ar) => { _sharingModality.EndDisconnect(ar); }, null);

            }
        }

        /// <summary>
        /// Accepts an invitation to connect to a resource sharing modality
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Acceptx_Button_Click(object sender, EventArgs e)
        {
            _sharingModality.Accept();
        }

        /// <summary>
        /// Rejects an invitiation to connect to a resource sharing modality
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void RejectX_Button_Click(object sender, EventArgs e)
        {
            _sharingModality.Reject(ModalityDisconnectReason.Decline);
        }

        /// <summary>
        /// Updates the locally shareable resource list with the newest
        /// list of locally shareable resources
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void RefreshResource_Button_Click(object sender, EventArgs e)
        {
            UpdateSharedResourcesListbox();
        }

        #endregion

        #region Client event handlers

        /// <summary>
        /// Handles the event raised when a user signs in to or out of the Lync client.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _LyncClient_StateChanged(object sender, ClientStateChangedEventArgs e)
        {

            //If the client has signed in then get the client's contact list and enable the conversation start button.
            if (e.NewState == ClientState.SignedIn)
            {
                this.Invoke(new LoadAllContactsDelegate(LoadAllContacts));
                this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Start_Button, true });
                this.Invoke(new UpdateSharedResourcesListboxDelegate(UpdateSharedResourcesListbox));

            }
            else
            {
                this.Invoke(new ClearAllContactsDelegate(ClearAllContacts));
                this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Start_Button, false });

                this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { ClientStateString_Label, e.NewState.ToString() });
                this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { EndConversation_Button, false });
                this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { StartSharingResource_Button, false });

            }
        }
        #endregion

        #region conversation manager event handlers
        /// <summary>
        /// Handles the event raised when the active conversation is terminated and removed from the collection of conversations
        /// on ConversationManager.Conversations
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void ConversationManager_ConversationRemoved(object sender, ConversationManagerEventArgs e)
        {
            this.Invoke(new SetContactSelectionModeDelegate(SetContactSelectionMode), new object[] { SelectionMode.MultiSimple });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { EndConversation_Button, false });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Disconnect_Button, false });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Request_Button, false });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { StartSharingResource_Button, false });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Start_Button, true });
            this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { ContactList_Label, "1) Choose contacts" });
            this.Invoke(new UpdateSharedResourcesListboxDelegate(UpdateSharedResourcesListbox));

            this.Invoke(new LoadAllContactsDelegate(LoadAllContacts));

            //Un-register for participant events on the conversation that is terminated.
            _conversation.ParticipantAdded -= _conversation_ParticipantAdded;
            _conversation.ParticipantRemoved -= _conversation_ParticipantRemoved;
            _conversation.StateChanged -= _conversation_StateChanged;

            //Unregister for events on the terminated conversation's sharing modality events.
            _sharingModality.ModalityStateChanged -= _sharingModality_ModalityStateChanged;
            _sharingModality.ControlRequestReceived -= _sharingModality_ControlRequestReceived;
            _sharingModality.LocalSharedResourcesChanged -= _sharingModality_LocalSharedResourcesChanged;
            _sharingModality.ControllerChanged -= _sharingModality_ControllerChanged;
            _sharingModality.ActionAvailabilityChanged -= _sharingModality_ActionAvailabilityChanged;

            //Unregister for the application sharing events on each and every participant in the terminated 
            //conversation
            foreach (string contactUri in _selectedContacts.Keys)
            {
                ApplicationSharingModality participantSharingModality = (ApplicationSharingModality)_participantSharingModalities[contactUri];
                participantSharingModality.ActionAvailabilityChanged -= _sharingModality_ActionAvailabilityChanged;
            }

            //If the removed conversation is the conversation hosted by this window then resume listening for new conversations.
            if (_conversation == e.Conversation)
            {
                //Resume listening for new conversations
                _LyncClient.ConversationManager.ConversationAdded += ConversationManager_ConversationAdded;
            }

            //de-reference the class state
            _conversation = null;
            _ResourceControllingContact = null;
            _sharingModality = null;
            _participantSharingModalities.Clear();

        }

        /// <summary>
        /// Handles the event raised when a new conversation is added. This sample only hosts one conversation
        /// at a time. Once this event is handled, the sample unregisters for this event. The event is registered again when
        /// this conversation is removed from the ContactManager.Conversations collection upon termination of this conversation.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void ConversationManager_ConversationAdded(object sender, Microsoft.Lync.Model.Conversation.ConversationManagerEventArgs e)
        {
            Boolean addedByThisProcess = true;

            try
            {
                //Suspend hosting new conversations until this conversation is ended
                _LyncClient.ConversationManager.ConversationAdded -= ConversationManager_ConversationAdded;
            }

            catch (Exception ex) { MessageBox.Show("Exception on de-register for ConversationAdded: " + ex.Message); }

            //If this class field is null then the new conversation was not started by this running process. It was
            //Started by the Lync client or by a remote user.
            if (_conversation == null)
            {
                addedByThisProcess = false;
                _conversation = e.Conversation;
            }

            //Register for conversation state changes such as Active->Terminated.
            _conversation.StateChanged += _conversation_StateChanged;

            //Register for the application sharing modality event on the conversation itself
            _sharingModality = (ApplicationSharingModality)_conversation.Modalities[ModalityTypes.ApplicationSharing];

            //Register for state changes like connecting->connected
            _sharingModality.ModalityStateChanged += _sharingModality_ModalityStateChanged;

            //Register to catch requests from other participants for control of the locally owned sharing resource.
            _sharingModality.ControlRequestReceived += _sharingModality_ControlRequestReceived;
            _sharingModality.ControllerChanged += _sharingModality_ControllerChanged;

            //Register to catch changes in the list of local sharable resources such as a process that starts up or terminates.
            _sharingModality.LocalSharedResourcesChanged += _sharingModality_LocalSharedResourcesChanged;

            //Register for changes in the availability of resource controlling actions such as grant and revoke.
            _sharingModality.ActionAvailabilityChanged += _sharingModality_ActionAvailabilityChanged;

            //Register for changes in the local participant's mode of sharing participation
            // such as Viewing->Sharing, Requesting Control->Controlling.
            _sharingModality.ParticipationStateChanged += _sharingModality_ParticipationStateChanged;

            //Register for participant added events on the new conversation
            //The next important action in the chain of conversation initiating action happens in the ParticipantAdded event handler.
            _conversation.ParticipantAdded += _conversation_ParticipantAdded;
            _conversation.ParticipantRemoved += _conversation_ParticipantRemoved;


            if (addedByThisProcess == true)
            {
                Contact aContact;

                //Clear out the contact list on the UI to be replaced with only the contacts selected for the current conversation.
                this.Invoke(new ClearAllContactsDelegate(ClearAllContacts));

                //Iterate on the contact dictionary that is filled from the contact Sip addresses selected from the 
                //contact list UI control. Add each selected contact to the conversation, causing an invitation to be
                //sent to each contact.
                foreach (Contact selectedContact in _selectedContacts.Values)
                {
                    Participant newParticipant =  _conversation.AddParticipant(selectedContact);

                    //Register for events on the conversation participant's application sharing modality
                    ((ApplicationSharingModality)newParticipant.Modalities[ModalityTypes.ApplicationSharing]).ActionAvailabilityChanged += _sharingModality_ActionAvailabilityChanged;

               //     this.Invoke(new AddAContactDelegate(AddAContact), new object[] { selectedContact.Uri });
                }
            }

            //Update the list of local sharable resources on the UI
            this.Invoke(new UpdateSharedResourcesListboxDelegate(UpdateSharedResourcesListbox));

            //Set the enabled state of the resource sharing button, end conversation button, and start conversation button.
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { StartSharingResource_Button, true });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { EndConversation_Button, true });
            this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { Start_Button, false });

            ((InstantMessageModality)_conversation.Modalities[ModalityTypes.InstantMessage]).BeginSendMessage("hi", (ar) => {

                ((InstantMessageModality)_conversation.Modalities[ModalityTypes.InstantMessage]).EndSendMessage(ar);
            }, null);

        }
        #endregion

        #region Conversation event handlers

        /// <summary>
        /// Handles the event raised when a conversation becomes active or is terminated.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _conversation_StateChanged(object sender, ConversationStateChangedEventArgs e)
        {
        }

        /// <summary>
        /// Handles the participant added event. Registers for events on the application sharing modality for the 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _conversation_ParticipantAdded(object sender, ParticipantCollectionChangedEventArgs e)
        {
            //Is this added participant the local user?
            if (e.Participant.IsSelf)
            {
                //Store the application sharing modality of the local user so that
                //the user can request or release control of a remotely owned and shared resource.
                _LocalParticipantSharingModality = (ApplicationSharingModality)e.Participant.Modalities[ModalityTypes.ApplicationSharing];

                //Enable or disable the Start Resource Sharing button according to the role of the local participant.
                //Roles can be Presenter or Attendee.

                if (e.Participant.Properties[ParticipantProperty.IsPresenter] != null)
                { 
                     this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { StartSharingResource_Button, (Boolean)e.Participant.Properties[ParticipantProperty.IsPresenter] });
                }
                //Register for the particpant property changed event to be notified when the role of the local user changes.
                e.Participant.PropertyChanged += Participant_PropertyChanged;

                this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharingParticipationStateString_Label, "not sharing" });

            }

            //Get the application sharing modality of the added participant and store it in a class dictionary field for easy access later.
            ApplicationSharingModality participantSharingModality = (ApplicationSharingModality)e.Participant.Modalities[ModalityTypes.ApplicationSharing];
            _participantSharingModalities.Add(e.Participant.Contact.Uri, participantSharingModality);

            //register for important events on the application sharing modality of the new participant.
            participantSharingModality.ActionAvailabilityChanged += _sharingModality_ActionAvailabilityChanged;
            participantSharingModality.ModalityStateChanged += _sharingModality_ModalityStateChanged;

        }

        /// <summary>
        /// Handles the event raised when a participant is removed from the conversation.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _conversation_ParticipantRemoved(object sender, ParticipantCollectionChangedEventArgs e)
        {

            //get the application sharing modality of the removed participant out of the class modality dictionary
            ApplicationSharingModality removedModality = _participantSharingModalities[e.Participant.Contact.Uri];

            //Unregister for modality events on this participant's application sharing modality.
            removedModality.ActionAvailabilityChanged -= _sharingModality_ActionAvailabilityChanged;

            //Remove the modality from the dictionary.
            _participantSharingModalities.Remove(e.Participant.Contact.Uri);
            this.Invoke(new RemoveAContactDelegate(RemoveAContact), new object[] { e.Participant.Contact.Uri});
        }
        #endregion

        #region Participant event handlers
        /// <summary>
        /// Called when a participant property is changed.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void Participant_PropertyChanged(object sender, ParticipantPropertyChangedEventArgs e)
        {
            if (e.Property == ParticipantProperty.IsPresenter)
            {
                //Enable or disable the Start Sharing Resource button according to the participant role
                this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { StartSharingResource_Button, (Boolean)e.Value });
            }
        }

        #endregion

        #region application sharing modality event handlers

        /// <summary>
        /// Handles the event raised when the local user has started or ended a shareable process.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_LocalSharedResourcesChanged(object sender, LocalSharedResourcesChangedEventArgs e)
        {
            //Update the shareable resources list box with the currently available shareable resources.
            if (e.ResourceList.Count > 0)
            {
                this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharedResource_Label, e.ResourceList[0].Name });
            }
            else
            {
                this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharedResource_Label, "None" });
            }
        }

        /// <summary>
        /// Handles the even raised when the state of an application sharing modality changes.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ModalityStateChanged(object sender, ModalityStateChangedEventArgs e)
        {

            //Modality will be connected for each participant whether they have accepted the sharing invite or not.
            
            ApplicationSharingModality thisModality = (ApplicationSharingModality)sender;
            if (e.NewState == ModalityState.Connected)
            {
                this.Invoke(new AddAContactDelegate(AddAContact), new object[] { thisModality.Participant.Contact.Uri });
                this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { ContactList_Label, "5) Pick a participant" });
            }
        }

        /// <summary>
        /// Handles the event raised when the participant that is controlling the shared conversation application resource
        /// changes. This event is raised locally even when the shared resource is not locally owned.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ControllerChanged(object sender, ControllerChangedEventArgs e)
        {
            this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { ResourceControllerName_Label, e.ControllerName });

            //Store the Contact object for the conversation participant that now controls the shared conversation resource.
            if (((ApplicationSharingModality)sender).Controller != null)
            {
                _ResourceControllingContact = ((ApplicationSharingModality)sender).Controller.Contact;
            }

        }

        /// <summary>
        /// Handles the event raised when a conversation participant requests control of a locally owned resource.
        /// These requests always go to the resource owner and not the current controller of the resource.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ControlRequestReceived(object sender, ControlRequestReceivedEventArgs e)
        {
            //Get the name of the participant that is requesting control of the locally owned resource.
            string displayRequesterName = e.Requester.Contact.GetContactInformation(ContactInformationType.DisplayName).ToString();

            //Update the text of the Accept button to include the name of the requester.
            this.Invoke(new ChangeButtonTextDelegate(ChangeButtonText), new object[] { Accept_Button, "Accept " + displayRequesterName + "  Request" });

            //Store the Contact object for the requesting participant.
            _ResourceControllingContact = e.Requester.Contact;
        }

        /// <summary>
        /// Handles the event raised when a participant participation state changes.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ParticipationStateChanged(object sender, ParticipationStateChangedEventArgs e)
        {
            if (((ApplicationSharingModality)sender) == _sharingModality)
            {
                if (e.NewState.ToString() == "None")
                {
                    this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharingParticipationStateString_Label, "not sharing" });
                }
                else
                {
                    this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharingParticipationStateString_Label, e.NewState.ToString() });

                }
                ApplicationSharingModality participantModality = (ApplicationSharingModality)sender;
                if (participantModality.Controller != null)
                {
                    string userName = participantModality.Controller.Contact.GetContactInformation(ContactInformationType.DisplayName).ToString();
                    this.Invoke(new ChangeLabelTextDelegate(ChangeLabelText), new object[] { SharedResource_Label, userName });
                }
            }
        }

        /// <summary>
        /// Event handler for sharing modality action availability change
        /// This method enables or disables the modality control action buttons on the UI according to
        /// the availability of a given action.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void _sharingModality_ActionAvailabilityChanged(object sender, ModalityActionAvailabilityChangedEventArgs e)
        {
            try
            {
                ApplicationSharingModality thisModality = (ApplicationSharingModality)sender;
                Button buttonToUpdate = null;

                //Enable or disable a UI action button that corresponds to the action whose availability has changed.
                switch (e.Action)
                {
                    case ModalityAction.Accept:
                        buttonToUpdate = Acceptx_Button;
                        break;
                    case ModalityAction.Reject:
                        buttonToUpdate = RejectX_Button;
                        break;
                    case ModalityAction.AcceptSharingControlRequest:
                        buttonToUpdate = Accept_Button;
                        break;
                    case ModalityAction.DeclineSharingControlRequest:
                        buttonToUpdate = Decline_Button;
                        break;
                    case ModalityAction.GrantSharingControl:
                        buttonToUpdate = Grant_Button;
                        break;
                    case ModalityAction.ReleaseSharingControl:
                        buttonToUpdate = Release_Button;
                        break;
                    case ModalityAction.RequestSharingControl:
                        buttonToUpdate = Request_Button;
                        break;
                    case ModalityAction.RevokeSharingControl:
                        buttonToUpdate = Revoke_Button;
                        break;
                    case ModalityAction.Disconnect:
                        buttonToUpdate = Disconnect_Button;
                        break;
                }

                //Not all possible cases of ActionAvailability are represented in the previous switch statement. 
                //For this reason, buttonToUpdate may be null.
                if (buttonToUpdate != null)
                {
                    this.Invoke(new EnableDisableButtonDelegate(EnableDisableButton), new object[] { buttonToUpdate, e.IsAvailable });
                }
            }
            catch (Exception)  { }
        }
        #endregion

        #region API Operation callback methods

        /// <summary>
        /// Completes the desktop sharing operation.
        /// </summary>
        /// <param name="ar"></param>
        private void ShareDesktopCallback(System.IAsyncResult ar)
        {
            try
            {
                ApplicationSharingModality sharingModality = (ApplicationSharingModality)ar.AsyncState;
                sharingModality.EndShareDesktop(ar);
            }
            catch (LyncClientException )  {}
            catch (InvalidCastException) { };
        }

        /// <summary>
        /// Completes the process sharing operation
        /// </summary>
        /// <param name="ar"></param>
        private void ShareResourcesCallback(System.IAsyncResult ar)
        {
            try
            {
                ((ApplicationSharingModality)ar.AsyncState).EndShareResources(ar);
            }
            catch (OperationException) { }
            catch (LyncClientException ) {}
            catch (InvalidCastException) { };

        }

        /// <summary>
        /// Completes the monitor sharing operation
        /// </summary>
        /// <param name="ar"></param>
        private void ShareMonitorCallback(System.IAsyncResult ar)
        {
            try
            {
                ApplicationSharingModality sharingModality = (ApplicationSharingModality)ar.AsyncState;
                sharingModality.EndShareMonitor(ar);
            }
            catch (InvalidCastException ) {}
            catch (LyncClientException )  {}

        }

        #endregion

        #region UI update helper methods and their delegates

        /// <summary>
        /// Shares the resource selected by the user.
        /// </summary>
        private void ShareSelectedResource(Int32 selectedResource)
        {

            //Get the type of resource selected by the user
            SharingResourceType selectedResourceType = ((SharingResource)_sharingModality.ShareableResources[selectedResource]).Type;

            CanShareDetail sharingDetail;
            if (!_sharingModality.CanShare(selectedResourceType, out sharingDetail))
            {
                switch (sharingDetail)
                {
                    case CanShareDetail.DisabledByOrganizerPolicy:
                        MessageBox.Show("The conversation organizer has disallowed sharing" );
                        break;
                    case CanShareDetail.DisabledByPolicy:
                        MessageBox.Show("Sharing resources is not allowed ");
                        break;
                    case CanShareDetail.DisabledByRole:
                        MessageBox.Show("Conference attendees cannot share resources" );
                        break;
                }
                return;
            }

            switch (selectedResourceType)
            {
                case SharingResourceType.Desktop:
                    _sharingModality.BeginShareDesktop((ar) => 
                        {
                            _sharingModality.EndShareDesktop(ar);
                        }
                        , null);
                    break;
                case SharingResourceType.Monitor:

                    //Share the primary monitor
                    //Iterate on all system displays and find the primary display
                    for (int i = 0; i < System.Windows.Forms.Screen.AllScreens.Length; i++)
                    {
                        //If this screen is the primary display, 
                        if (((Screen)System.Windows.Forms.Screen.AllScreens[i]).Primary)
                        {
                            //Share the primary display using a 1-based index value
                            _sharingModality.BeginShareMonitor(i + 1, (ar) => 
                                {
                                    try
                                    {
                                        _sharingModality.EndShareMonitor(ar);
                                    }
                                    catch (LyncClientException lce) { throw lce; }
                                }
                                , null);
                        }
                    }
                    break;
                case SharingResourceType.Process:

                    _sharingModality.BeginShareResources((SharingResource)_sharingModality.ShareableResources[selectedResource], (ar) => 
                        {
                            try
                            {
                                _sharingModality.EndShareResources(ar);
                            }
                            catch (OperationException oe) { throw oe; }
                            catch (LyncClientException lce) { throw lce; }
                        }
                        , null);
                    break;
            }
        }

        private delegate void EnableDisableButtonDelegate(Button buttonToUpdate, Boolean newButtonEnableState);

        /// <summary>
        /// Enables or disables a UI button based on the actionAvailability
        /// </summary>
        /// <param name="buttonToUpdate"></param>
        /// <param name="newButtonEnableState"></param>
        private void EnableDisableButton(Button buttonToUpdate, Boolean newButtonEnableState)
        {
            buttonToUpdate.Enabled = newButtonEnableState;
        }

        private delegate void LoadAllContactsDelegate();

        /// <summary>
        /// Iterates on all groups and adds an Uri string for each contact in a group to a list on the UI
        /// </summary>
        private void LoadAllContacts()
        {
            //Set the selection mode of the UI list to multi-select
            Contact_ListBox.SelectionMode = SelectionMode.MultiSimple;
            Contact_ListBox.Items.Clear();
            foreach (Group group in _LyncClient.ContactManager.Groups)
            {
                foreach (Contact contact in group)
                {
                    if (!Contact_ListBox.Items.Contains(contact.Uri))
                       Contact_ListBox.Items.Add(contact.Uri);
                }
            }
        }

        private delegate void ClearAllContactsDelegate();
        private void ClearAllContacts()
        {
            Contact_ListBox.Items.Clear();
        }

        private delegate void AddAContactDelegate(string ContactUri);
        private void AddAContact(string ContactUri)
        {
            Contact_ListBox.SelectionMode = SelectionMode.One;
            if (!Contact_ListBox.Items.Contains(ContactUri))
            {
                Contact_ListBox.Items.Add(ContactUri);
            }
        }

        private delegate void RemoveAContactDelegate(string ContactUri);
        private void RemoveAContact(string ContactUri)
        {
            Contact_ListBox.Items.Remove(ContactUri);
        }

        private delegate void UpdateSharedResourcesListboxDelegate();

        /// <summary>
        /// Fills a UI list with the names of all local resources that can be shared.
        /// </summary>
        private void UpdateSharedResourcesListbox()
        {
            SharedResources_ListBox.Items.Clear();
            if (_sharingModality == null || _sharingModality.ShareableResources == null)
            {
                return;
            }
            if (_sharingModality.ShareableResources.Count > 0)
            {
                SharingResource sharingResource;
                for (int j = 0; j < _sharingModality.ShareableResources.Count; j++)
                {
                    sharingResource = _sharingModality.ShareableResources[j];
                    SharedResources_ListBox.Items.Add(sharingResource.Name);
                }
            }
        }

        private delegate void ChangeButtonTextDelegate(Button buttonToChange, string newText);
        private void ChangeButtonText(Button buttonToChange, string newText)
        {
            buttonToChange.Text = newText;
        }

        private delegate void SetContactSelectionModeDelegate(SelectionMode newMode);
        /// <summary>
        /// Changes the contact list on the UI from single-select to multi-select mode
        /// </summary>
        /// <param name="newMode"></param>
        private void SetContactSelectionMode(SelectionMode newMode)
        {
            Contact_ListBox.SelectionMode = newMode;
        }

        private delegate void ChangeLabelTextDelegate(Label labelToUpdate, string newText);
        /// <summary>
        /// Replaces the text of any label control on the UI with new text
        /// </summary>
        /// <param name="labelToUpdate"></param>
        /// <param name="newText"></param>
        private void ChangeLabelText(Label labelToUpdate, string newText)
        {
            labelToUpdate.Text = newText;
        }

        #endregion

        #region constructors
        public ShareResources_Form()
        {
            InitializeComponent();
        }
        #endregion

    }
}

Read the following topics to learn about requesting control of a resource that another conversation participant is sharing. You also learn how to handle a request from another participant to control a locally shared resource.

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