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Form.OnClosing(CancelEventArgs) Method

  • Reference

Definition

Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms.dll
Source:
Form.cs
Source:
Form.cs
Source:
Form.cs

Raises the Closing event.

protected:
 virtual void OnClosing(System::ComponentModel::CancelEventArgs ^ e);
protected virtual void OnClosing (System.ComponentModel.CancelEventArgs e);
abstract member OnClosing : System.ComponentModel.CancelEventArgs -> unit
override this.OnClosing : System.ComponentModel.CancelEventArgs -> unit
Protected Overridable Sub OnClosing (e As CancelEventArgs)

Parameters

e
CancelEventArgs

A CancelEventArgs that contains the event data.

Examples

The following example uses Closing to test if the text in a TextBox has changed. If it has, the user is asked whether to save the changes to a file.

private:
   void Form1_Closing( Object^ /*sender*/, System::ComponentModel::CancelEventArgs^ e )
   {
      // Determine if text has changed in the textbox by comparing to original text.
      if ( textBox1->Text != strMyOriginalText )
      {
         // Display a MsgBox asking the user to save changes or abort.
         if ( MessageBox::Show( "Do you want to save changes to your text?", "My Application", MessageBoxButtons::YesNo ) == ::DialogResult::Yes )
         {
            // Cancel the Closing event from closing the form.
            e->Cancel = true;

            // Call method to save file...
         }
      }
   }

private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
   // Determine if text has changed in the textbox by comparing to original text.
   if (textBox1.Text != strMyOriginalText)
   {
      // Display a MsgBox asking the user to save changes or abort.
      if(MessageBox.Show("Do you want to save changes to your text?", "My Application",
         MessageBoxButtons.YesNo) ==  DialogResult.Yes)
      {
         // Cancel the Closing event from closing the form.
         e.Cancel = true;
         // Call method to save file...
      }
   }
}

   Private Sub Form1_Closing(sender As Object, e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
      ' Determine if text has changed in the textbox by comparing to original text.
      If textBox1.Text <> strMyOriginalText Then
         ' Display a MsgBox asking the user to save changes or abort.
         If MessageBox.Show("Do you want to save changes to your text?", "My Application", MessageBoxButtons.YesNo) = DialogResult.Yes Then
            ' Cancel the Closing event from closing the form.
            e.Cancel = True
         End If ' Call method to save file...
      End If
   End Sub
End Class

Remarks

Caution

The OnClosing method is obsolete starting with the .NET Framework 2.0; use the OnFormClosing method instead.

Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.

The OnClosing method also allows derived classes to handle the event without attaching a delegate. Overriding this method is the preferred technique for handling the event in a derived class.

Caution

The OnClosed and OnClosing methods are not called when the Application.Exit method is called to exit your application. If you have validation code in either of these methods that must be executed, you should call the Form.Close method for each open form individually before calling the Exit method.

Notes to Inheritors

When overriding OnClosing(CancelEventArgs) in a derived class, be sure to call the base class's OnClosing(CancelEventArgs) method so that registered delegates receive the event.

Applies to

See also