Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms (in System.Windows.Forms.dll)
Visual Basic (Declaration)
Protected Overridable Sub OnClosing ( _
e As CancelEventArgs _
)
Dim e As CancelEventArgs
Me.OnClosing(e)
protected virtual void OnClosing(
CancelEventArgs e
)
protected:
virtual void OnClosing(
CancelEventArgs^ e
)
protected function OnClosing(
e : CancelEventArgs
)
.gif) Caution: |
|---|
The OnClosing method is obsolete in the .NET Framework version 2.0; use the OnFormClosing method instead.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 Raising an Event.
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. |
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
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...
}
}
}
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
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
Reference