CancelEventArgs Class
Provides data for a cancelable event.
For a list of all members of this type, see CancelEventArgs Members.
System.Object
System.EventArgs
System.ComponentModel.CancelEventArgs
System.Drawing.Printing.PrintEventArgs
System.Windows.Forms.InputLanguageChangingEventArgs
System.Windows.Forms.TreeViewCancelEventArgs
[Visual Basic] Public Class CancelEventArgs Inherits EventArgs [C#] public class CancelEventArgs : EventArgs [C++] public __gc class CancelEventArgs : public EventArgs [JScript] public class CancelEventArgs extends EventArgs
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Remarks
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.
A CancelEventArgs provides the Cancel property to indicate whether the event should be canceled.
Example
[Visual Basic, C#, C++] The following example uses a 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 myDataIsSaved.
[Visual Basic] ' Calls this method from the InitializeComponent() method of your form. Private Sub OtherInitialize() AddHandler Me.Closing, AddressOf Me.Form1_Cancel Me.myDataIsSaved = New Boolean() Me.myDataIsSaved = True End Sub 'OtherInitialize Protected Sub Form1_Cancel(sender As Object, e As CancelEventArgs) If Not myDataIsSaved Then e.Cancel = True MessageBox.Show("You must save first.") Else e.Cancel = False MessageBox.Show("Goodbye.") End If End Sub 'Form1_Cancel [C#] // Calls this method from the InitializeComponent() method of your form private void OtherInitialize() { this.Closing += new CancelEventHandler(this.Form1_Cancel); this.myDataIsSaved = new Boolean(); this.myDataIsSaved = true; } protected void Form1_Cancel (Object sender, CancelEventArgs e) { if (!myDataIsSaved) { e.Cancel = true; MessageBox.Show("You must save first."); } else { e.Cancel = false; MessageBox.Show("Goodbye."); } } [C++] // Calls this method from the InitializeComponent() method of your form private: void OtherInitialize() { this->Closing += new CancelEventHandler(this, &Form1::Form1_Cancel); this->myDataIsSaved = true; } protected: void Form1_Cancel (Object* /*sender*/, CancelEventArgs* e) { if (!myDataIsSaved) { e->Cancel = true; MessageBox::Show(S"You must save first."); } else { e->Cancel = false; MessageBox::Show(S"Goodbye."); } }
[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button
in the upper-left corner of the page.
Requirements
Namespace: System.ComponentModel
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework
Assembly: System (in System.dll)
See Also
CancelEventArgs Members | System.ComponentModel Namespace | CancelEventHandler