ListControlDesigner Class

Definition

public ref class ListControlDesigner : System::Web::UI::Design::ControlDesigner, System::Web::UI::Design::IDataSourceProvider

public ref class ListControlDesigner : System::Web::UI::Design::WebControls::DataBoundControlDesigner

public class ListControlDesigner : System.Web.UI.Design.ControlDesigner, System.Web.UI.Design.IDataSourceProvider

[System.Web.UI.Design.SupportsPreviewControl(true)]
public class ListControlDesigner : System.Web.UI.Design.WebControls.DataBoundControlDesigner

type ListControlDesigner = class
    inherit ControlDesigner
    interface IDataSourceProvider

[<System.Web.UI.Design.SupportsPreviewControl(true)>]
type ListControlDesigner = class
    inherit DataBoundControlDesigner

Public Class ListControlDesigner
Inherits ControlDesigner
Implements IDataSourceProvider

Public Class ListControlDesigner
Inherits DataBoundControlDesigner

Inheritance

Object

ComponentDesigner

HtmlControlDesigner

ControlDesigner

ListControlDesigner

Inheritance

Object

ComponentDesigner

HtmlControlDesigner

ControlDesigner

BaseDataBoundControlDesigner

DataBoundControlDesigner

ListControlDesigner

Derived

System.Web.UI.Design.WebControls.BulletedListDesigner

Attributes

SupportsPreviewControlAttribute

Implements

IDataSourceProvider

Examples

This section provides two code examples. The first demonstrates how to derive a custom control designer. The second demonstrates how to associate a derived control with a designer.

The following code example shows how to create a class named SimpleRadioButtonListDesigner that inherits from the ListControlDesigner class. The SimpleRadioButtonListDesigner class overrides the GetDesignTimeHtml, Initialize, and OnDataSourceChanged methods. The SimpleRadioButtonListDesigner class displays a SimpleRadioButtonList control on the design surface.

using System;
using System.ComponentModel;
using System.Drawing;
using System.Diagnostics;
using System.Web.UI.WebControls;
using System.Web.UI.Design.WebControls;

namespace Examples.CS.WebControls.Design
{
    // Create the SimpleRadioButtonListDesigner, which provides
    // design-time support for a custom list class.
    public class SimpleRadioButtonListDesigner : ListControlDesigner
    {
        SimpleRadioButtonList simpleRadioButtonList;
        bool changedDataSource;

        // Create the markup to display the control on the design surface. 
        public override string GetDesignTimeHtml()
        {
            string designTimeMarkup = null;

            // Create variables to access the control
            // item collection and back color.
            ListItemCollection items = simpleRadioButtonList.Items;
            Color oldBackColor = simpleRadioButtonList.BackColor;

            // Check the property values and render the markup
            // on the design surface accordingly.
            try
            {
                if (oldBackColor == Color.Empty)
                    simpleRadioButtonList.BackColor = Color.Gainsboro;

                if (changedDataSource)
                    items.Add("Updated to a new data source: " + 
                        DataSource + ".");

                // Call the base method to generate the markup.
                designTimeMarkup = base.GetDesignTimeHtml();
            }
            catch (Exception ex)
            {
                // Catch any exceptions that occur.
                designTimeMarkup = GetErrorDesignTimeHtml(ex);
            }
            finally
            {
                // Set the properties back to their original state.
                simpleRadioButtonList.BackColor = oldBackColor;
                items.Clear();
            }

            return designTimeMarkup;
        } // GetDesignTimeHtml

        public override void Initialize(IComponent component)
        {
            // Ensure that only a SimpleRadioButtonList can be 
            // created in this designer.
            Debug.Assert( 
                component is SimpleRadioButtonList, 
                "An invalid SimpleRadioButtonList control was initialized.");

            simpleRadioButtonList = (SimpleRadioButtonList)component;
            base.Initialize(component);
        } // Initialize

        // If the data source changes, set a boolean variable.
        public override void OnDataSourceChanged()
        {
            changedDataSource = true;
        } // OnDataSourceChanged
    } // SimpleRadioButtonListDesigner
} // Examples.CS.WebControls.Design

Imports System.ComponentModel
Imports System.Drawing
Imports System.Diagnostics
Imports System.Web.UI.WebControls
Imports System.Web.UI.Design.WebControls

Namespace Examples.VB.WebControls.Design

    ' Create the SimpleRadioButtonListDesigner, which provides
    ' design-time support for a custom list class.  
    Public Class SimpleRadioButtonListDesigner
        Inherits ListControlDesigner

        Private simpleRadioButtonList As SimpleRadioButtonList
        Private changedDataSource As Boolean

        ' Create the markup to display the control on the design surface.
        Public Overrides Function GetDesignTimeHtml() As String

            Dim designTimeHtml As String = String.Empty

            ' Create variables to access the control's
            ' item collection and back color. 
            Dim items As ListItemCollection = simpleRadioButtonList.Items
            Dim oldBackColor As Color = simpleRadioButtonList.BackColor

            ' Check the property values and render the markup
            ' on the design surface accordingly.
            Try
                If (Color.op_Equality(oldBackColor, Color.Empty)) Then
                    simpleRadioButtonList.BackColor = Color.Gainsboro
                End If

                If (changedDataSource) Then
                    items.Add( _
                        "Updated to a new data source: " & DataSource & ".")
                End If

                designTimeHtml = MyBase.GetDesignTimeHtml()

            Catch ex As Exception
                ' Catch any exceptions that occur.
                MyBase.GetErrorDesignTimeHtml(ex)

            Finally
                ' Set the properties back to their original state.
                simpleRadioButtonList.BackColor = oldBackColor
                items.Clear()
            End Try

            Return designTimeHtml
        End Function ' GetDesignTimeHtml

        Public Overrides Sub Initialize(ByVal component As IComponent)

            ' Ensure that only a SimpleRadioButtonList can be created 
            ' in this designer.
            Debug.Assert( _
                TypeOf component Is SimpleRadioButtonList, _
                "An invalid SimpleRadioButtonList control was initialized.")

            simpleRadioButtonList = CType(component, SimpleRadioButtonList)
            MyBase.Initialize(component)
        End Sub

        ' If the data source changes, set a Boolean variable.
        Public Overrides Sub OnDataSourceChanged()
            changedDataSource = True
        End Sub
    End Class
End Namespace ' Examples.VB.WebControls.Design

The following code example derives the SimpleRadioButtonList control from the RadioButtonList control, and shows how to use the DesignerAttribute class to associate the SimpleRadioButtonList control with its designer, the SimpleRadioButtonListDesigner class.

using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Security.Permissions;

namespace Examples.CS.WebControls.Design
{
    // The SimpleRadioButtonList is a copy of the RadioButtonList.
    // It uses the SimpleRadioButtonListDesigner for design-time support.
    [AspNetHostingPermission(SecurityAction.Demand, 
        Level = AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, 
        Level = AspNetHostingPermissionLevel.Minimal)]
    [Designer(typeof(Examples.CS.WebControls.Design.
       SimpleRadioButtonListDesigner))]
    [DataBindingHandler(typeof(Examples.CS.WebControls.Design.
        SimpleRadioButtonListDataBindingHandler))]
    public class SimpleRadioButtonList : RadioButtonList
    {
    } // SimpleRadioButtonList
} // Examples.CS.WebControls.Design

Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.ComponentModel
Imports System.Security.Permissions

Namespace Examples.VB.WebControls.Design

    ' The SimpleRadioButtonList is a copy of the RadioButtonList.
    ' It uses the SimpleRadioButtonListDesigner for design-time support.
    <AspNetHostingPermission(SecurityAction.Demand, _
        Level:=AspNetHostingPermissionLevel.Minimal)> _
    <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
        Level:=AspNetHostingPermissionLevel.Minimal)> _
    <DesignerAttribute(GetType(Examples.VB.WebControls.Design. _
        SimpleRadioButtonListDesigner))> _
    <DataBindingHandler(GetType(Examples.VB.WebControls.Design. _
        SimpleRadioButtonListDataBindingHandler))> _
    Public Class SimpleRadioButtonList
        Inherits RadioButtonList
    End Class
End Namespace ' Examples.VB.WebControls.Design

Remarks

In the Visual Web Designer, when the user switches from Source to Design view, the markup source code that describes a control derived from the ListControl class is parsed and a design-time version of the control is created on the design surface. When the user switches back to Source view, the design-time control is persisted to the markup source code and edited into the markup for the Web page. The ListControlDesigner class serves as the base class for designers that provide design-time support in the Visual Web Designer for controls that are derived from the ListControl.

The ListControlDesigner class properties provide the following functionality:

• The ActionLists property returns a DesignerActionListCollection object, which typically contains an object that is derived from the DesignerActionList object for each level in the inheritance tree of the designer.

• The DataTextField and DataValueField properties provide access to the corresponding properties of a control that is derived from the ListControl class. The DataTextField and DataValueField indicate the fields of the data source that provide the text and value content of the list items, respectively.

The ListControlDesigner class methods provide the following functionality:

• The DataBind method binds the associated control that is derived from the ListControl to a design-time data source.

• The GetDesignTimeHtml method returns the markup that is used to render the associated control at design time.

• The GetSelectedDataSource method returns the design-time DataSource component from the associated control container.

• The GetResolvedSelectedDataSource method returns the DataSource from the control container, resolved to the design-time DataMember property of the control.

• The Initialize method prepares the designer to view and design the associated control that is derived from the ListControl.

• The OnDataSourceChanged method is called when the DataSource for the associated control has changed.

• The PreFilterProperties method is used to remove additional properties from, add additional properties to, or shadow properties of the associated control that is derived from the ListControl.

Constructors

Properties

Methods

Explicit Interface Implementations

Applies to

See also

• ListControl
• DataBoundControl
• DataBoundControlDesigner
• BaseDataBoundControl
• BaseDataBoundControlDesigner
• WebControl
• ControlDesigner
• Introduction to ASP.NET Control Designers
• Walkthrough: Creating a Basic Control Designer for a Web Server Control