Microsoft KB Archive/168204

= How To Kill an Application with System Menu Using VB =

Article ID: 168204

Article Last Modified on 7/1/2004

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APPLIES TO


 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition

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This article was previously published under Q168204



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
 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. Create two Command Buttons called Command1 and Command2. On the Project menu, click Add Module (ALT, P, M). Module1 is created by default.  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

  Within the Command1 Click event, add the following code: Private Sub Command1_Click Shell "Calc.exe", vbNormalFocus End Sub

  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

 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.</li></ol>

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