CancelEventArgs Class

Updated: August 2008

Provides data for a cancelable event.

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true)]
public class CancelEventArgs : EventArgs

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: SharedState. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

A cancelable event is raised by a component when it is about to perform an action that can be canceled, such as the Closing event of a Form.

NoteNote:

The Closing event is deprecated and has been replaced by FormClosing. It is offered as an example here only to illustrate the usage of CancelEventArgs.

CancelEventArgs provides the Cancel property to indicate whether the event should be canceled.

The following example uses CancelEventArgs and a CancelEventHandler to handle the Closing event of a Form. This code assumes that you have created a Form with a class-level Boolean variable named isDataSaved. It also assumes that you have added a statement to invoke the OtherInitialize method from the form's Load method or the constructor (after the call to InitializeComponent).

// Call this method from the constructor of your form 
    private void OtherInitialize() {
       this.Closing += new CancelEventHandler(this.Form1_Closing);
       // Exchange commented line and note the difference. 
       this.isDataSaved = true;
       //this.isDataSaved = false;
    }

    private void Form1_Closing(Object sender, CancelEventArgs e) {
       if (!isDataSaved) {
          e.Cancel = true;
          MessageBox.Show("You must save first.");
       }
       else {
          e.Cancel = false;
          MessageBox.Show("Goodbye.");
       }
    }

System.Object
  System.EventArgs
    System.ComponentModel.CancelEventArgs
      Microsoft.VisualBasic.ApplicationServices.StartupEventArgs
      System.ComponentModel.DoWorkEventArgs
      System.Configuration.SettingChangingEventArgs
      System.Drawing.Printing.PrintEventArgs
      System.Web.UI.WebControls.DetailsViewDeleteEventArgs
      System.Web.UI.WebControls.DetailsViewInsertEventArgs
      System.Web.UI.WebControls.DetailsViewModeEventArgs
      System.Web.UI.WebControls.DetailsViewPageEventArgs
      System.Web.UI.WebControls.DetailsViewUpdateEventArgs
      System.Web.UI.WebControls.FormViewDeleteEventArgs
      System.Web.UI.WebControls.FormViewInsertEventArgs
      System.Web.UI.WebControls.FormViewModeEventArgs
      System.Web.UI.WebControls.FormViewPageEventArgs
      System.Web.UI.WebControls.FormViewUpdateEventArgs
      System.Web.UI.WebControls.GridViewCancelEditEventArgs
      System.Web.UI.WebControls.GridViewDeleteEventArgs
      System.Web.UI.WebControls.GridViewEditEventArgs
      System.Web.UI.WebControls.GridViewPageEventArgs
      System.Web.UI.WebControls.GridViewSelectEventArgs
      System.Web.UI.WebControls.GridViewSortEventArgs
      System.Web.UI.WebControls.GridViewUpdateEventArgs
      System.Web.UI.WebControls.LinqDataSourceDeleteEventArgs
      System.Web.UI.WebControls.LinqDataSourceDisposeEventArgs
      System.Web.UI.WebControls.LinqDataSourceInsertEventArgs
      System.Web.UI.WebControls.LinqDataSourceSelectEventArgs
      System.Web.UI.WebControls.LinqDataSourceUpdateEventArgs
      System.Web.UI.WebControls.ListViewCancelEventArgs
      System.Web.UI.WebControls.ListViewDeleteEventArgs
      System.Web.UI.WebControls.ListViewEditEventArgs
      System.Web.UI.WebControls.ListViewInsertEventArgs
      System.Web.UI.WebControls.ListViewSelectEventArgs
      System.Web.UI.WebControls.ListViewSortEventArgs
      System.Web.UI.WebControls.ListViewUpdateEventArgs
      System.Web.UI.WebControls.ObjectDataSourceDisposingEventArgs
      System.Web.UI.WebControls.ObjectDataSourceFilteringEventArgs
      System.Web.UI.WebControls.ObjectDataSourceMethodEventArgs
      System.Web.UI.WebControls.SqlDataSourceCommandEventArgs
      System.Web.UI.WebControls.SqlDataSourceFilteringEventArgs
      System.Web.UI.WebControls.WebParts.WebPartCancelEventArgs
      System.Web.UI.WebControls.WebParts.WebPartConnectionsCancelEventArgs
      System.Web.UI.WebControls.WebParts.WebPartDisplayModeCancelEventArgs
      System.Windows.Controls.InkCanvasSelectionChangingEventArgs
      System.Windows.Controls.InkCanvasSelectionEditingEventArgs
      System.Windows.Controls.InkCanvasStrokeErasingEventArgs
      System.Windows.Forms.BindingCompleteEventArgs
      System.Windows.Forms.ColumnReorderedEventArgs
      System.Windows.Forms.ColumnWidthChangingEventArgs
      System.Windows.Forms.DataGridViewCellCancelEventArgs
      System.Windows.Forms.DataGridViewCellValidatingEventArgs
      System.Windows.Forms.DataGridViewRowCancelEventArgs
      System.Windows.Forms.FormClosingEventArgs
      System.Windows.Forms.InputLanguageChangingEventArgs
      System.Windows.Forms.PopupEventArgs
      System.Windows.Forms.SplitterCancelEventArgs
      System.Windows.Forms.TabControlCancelEventArgs
      System.Windows.Forms.ToolStripDropDownClosingEventArgs
      System.Windows.Forms.TreeViewCancelEventArgs
      System.Windows.Forms.WebBrowserNavigatingEventArgs
      System.Windows.Navigation.NavigatingCancelEventArgs
      System.Windows.SessionEndingCancelEventArgs

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

August 2008

Added note about FormClosing.

Information enhancement.

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