Q168204: HOWTO: Kill an Application with System Menu Using VB

Article: Q168204
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVBDB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SUMMARY
=======

Microsoft Visual Basic for Windows can use the Microsoft Windows API SendMessage
function to close any active window that has a system menu (referred to as the
Control Box within Visual Basic for Windows) with the Close option.

MORE INFORMATION
================

This sample program uses the Windows API SendMessage function to post a message
to any window in the environment, provided the handle to the window is known.
The API FindWindow function is used to determine the handle associated with the
window the user wants to close. To use FindWindow, you must know either the
ClassName or the Caption (if any) of that window. Please see the REFERENCES
section below for more information.

Steps to Create Example Program
-------------------------------

1. Start Visual Basic and select Standard EXE. If Visual Basic is already
  running, click New Project on the File menu and select Standard EXE. Form1 is
  created by default.

2. Create two Command Buttons called Command1 and Command2.

3. On the Project menu, click Add Module (ALT, P, M). Module1 is created by
  default.

4. In the Declarations section, declare the following two API functions:

        Declare Function FindWindow _
         Lib "user32" Alias "FindWindowA" _
         (ByVal lpClassName As String, _
         ByVal lpWindowName As String) _
         As Long

        Declare Function SendMessage _
         Lib "user32" Alias "SendMessageA" _
         (ByVal hwnd As Long, _
         ByVal wMsg As Long, _
         ByVal wParam As Long, _
         lParam As Long) _
         As Long

5. Within the Command1 Click event, add the following code:

        Private Sub Command1_Click()
           Shell "Calc.exe", vbNormalFocus
        End Sub

6. Within the Command2 Click event, add the following code:

        Private Sub Command2_Click()
           Dim lpClassName As String
           Dim lpCaption As String
           Dim Handle As Long

           Const NILL = 0&
           Const WM_SYSCOMMAND = &H112
           Const SC_CLOSE = &HF060&

           lpClassName = "SciCalc"
           lpCaption = "Calculator"

        '* Determine the handle to the Calculator window.
           Handle = FindWindow(lpClassName$, lpCaption$)

        '* Post a message to Calc to end its existence.
           Handle = SendMessage(Handle, WM_SYSCOMMAND, SC_CLOSE, NILL)

        End Sub

7. On the Run menu, click Start or press the F5 key to start the program.
  Clicking the Command1 button starts a (new) instance of the Windows
  Calculator accessory. Clicking on the Command2 button kills an instance of
  the Calculator.

REFERENCES
==========

For more information on the FindWindow and SendMessage functions, query on the
following words in the Microsoft Knowledge Base:

  FindWindow and Visual Basic or SendMessage and Visual Basic

For information on a different sample application that returns assorted
information for a windowed application, please see the following article in the
Microsoft Knowledge Base:

  Q112649 : How to Get a Window's Class Name and Other Window Attributes

Additional query words: kbVBp500 kbVBp600 kbdse kbDSupport kbVBp

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Keywords          : kbGrpDSVBDB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type        : kbhowto

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