Tip 187: Determining Whether an Application Was Closed from the Control Menu

December 5, 1995

This article explains how to prevent the user of your Microsoft? Visual
Basic? application from unintentionally quitting the application.

The Query_Unload Event
When running an application, you can select the Close command from the
Control-menu box in the upper-left corner of a window to quit the
application. When running a Microsoft? Windows? 95based application,
you can click the Close button located at the right end of the title
bar. These actions terminate the application immediately.

In a Microsoft Visual Basic? application, the Query_Unload event is
triggered when the user tries to quit an application that is running. The
UnloadMode variable in the Query_Unload event indicates how this event was
triggered by containing one of the five following values:

Value  Description
0      The user chose the Close command on the Control-menu box.
1      The application used the Query_Unload method itself.
2      The operating system is being shut down.
3      The application is being shut down by the Task Manager.
4      An MDI form, which closes all child forms belonging to it, is
       being closed.

For example, when the user chooses the Close command from the Control-menu
box to quit an application, the UnloadMode variable contains a value of

Example Program
This program shows how to prevent a user from accidentally choosing the
Close command on the program's Control-menu box.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following code to the Query_Unload event for Form1:

Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    Dim I As Integer
    If (UnloadMode = FORM_CONTROLMENU) Then
        I = MsgBox("Exit " & App.Title & " ?", 4, App.EXEName)
        If I = 7 Then
            Cancel = True
            MsgBox "Program was not terminated"
        End If
        If I = 6 Then
            Cancel = False
            MsgBox "Program was terminated"
        End If
    End If
End Sub

Run the example program by pressing F5. Form1 appears on the screen.
Either click the File menu and click the Close command or click the
Close button in the upper right-hand corner of the form. The program
displays a message box asking whether you really want to quit the
program. If you click the Yes button, the program is immediately
terminated. If you click the No button, however, the program
continues to run.