Find out what's closing your application

Introduction

You can use this code to see why your application is closing (closed by user, by Windows, by code?). It can be very handy if you are using a NotifyIcon in your app. You can figure out if the user is closing your app or not, if so, then you can just minimize it to tray.

For those who have used Visual Basic before, you know that there was a QueryUnload method for your Forms and that you could find out the reason for the form's closing by examining the UnloadMode variable.

This code snippet shows you how to do this in .NET. The sample code is in VB.NET. The code is from GotDotNet message boards, written by "YeahIGotDotNet".

Private Sub Form1_Closing(ByVal sender As Object, _
  ByVal e As System.ComponentModel.CancelEventArgs) _
  Handles MyBase.Closing
    Dim O As System.Diagnostics.StackTrace = _
           New System.Diagnostics.StackTrace(True)
    Dim F As System.Diagnostics.StackFrame

    F = O.GetFrame(7)

    Select Case F.GetMethod.Name.ToString
        Case "SendMessage"
            MsgBox("Closing because of call in code.")
        Case "CallWindowProc"
            MsgBox("Closing because of system menu click.")
        Case "DispatchMessageW"
            MsgBox("Closing because of Task Manager.")
        Case Else
            MsgBox("Don't Know why I'm closing!!??")
    End Select
End Sub

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About the Author

MrPolite

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Handles Mybase.closing

atogwe

9:04 11 Jun '07

Using WM_QUERYENDSESSION to detect Windows shutdown

rodgerc

9:13 2 Oct '06

Overriding WndProc changes the GetMethod.Name properties

HanreG

3:15 7 Nov '03

Coversion of C++ method

BogBrush Zone

5:12 31 Aug '03

I have recently converted an application that does this from VC++/MFC to C#.   The following is a conversion of the method I used in that application by overriding OnSysCommand and essentially handling the event when it is a button press on the Close button/menu item and before it is translated into a request to close the window.

private const int WM_SYSCOMMAND = 0x0112;     // From winuser.h
private const int SC_CLOSE = 0xF060;

protected override void WndProc(ref Message m)
{
     if (m.Msg == WM_SYSCOMMAND && m.WParam.ToInt32() == SC_CLOSE)
     {
          // Perform actions
     }
     else
          base.WndProc (ref m);
}

N.B. I have also posted this to GotDotNet Wink | ;)