Form.OnClosing Method (CancelEventArgs)

 

Raises the Closing event.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

Protected Overridable Sub OnClosing (
	e As CancelEventArgs
)

Parameters

e
Type: System.ComponentModel.CancelEventArgs

A CancelEventArgs that contains the event data.

System_CAPS_cautionCaution

The OnClosing method is obsolete in the .NET Framework version 2.0; use the OnFormClosing method instead.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.

System_CAPS_cautionCaution

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

The following code 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 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 'Form1_Closing
End Class 'Form1

.NET Framework
Available since 1.1
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