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CancelEventArgs Class

.NET Framework (current version)

Other Versions

Provides data for a cancelable event.

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

Inheritance Hierarchy

Syntax

C++

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

Constructors

	Name	Description
	CancelEventArgs()	Initializes a new instance of the CancelEventArgs class with the Cancel property set to false.
	CancelEventArgs(Boolean)	Initializes a new instance of the CancelEventArgs class with the Cancel property set to the given value.

Properties

	Name	Description
	Cancel	Gets or sets a value indicating whether the event should be canceled.

Methods

	Name	Description
	Equals(Object^)	Determines whether the specified object is equal to the current object.(Inherited from Object.)
	Finalize()	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)
	GetHashCode()	Serves as the default hash function. (Inherited from Object.)
	GetType()	Gets the Type of the current instance.(Inherited from Object.)
	MemberwiseClone()	Creates a shallow copy of the current Object.(Inherited from Object.)
	ToString()	Returns a string that represents the current object.(Inherited from Object.)

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.

Note
The Closing event is deprecated and has been replaced by FormClosing.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).

C++

private:
   // Call this method from the InitializeComponent() method of your form
   void OtherInitialize()
   {
      this->Closing += gcnew CancelEventHandler( this, &Form1::Form1_Cancel );
      this->myDataIsSaved = true;
   }

   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." );
      }
   }

Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 3.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

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.

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