HOWTO: Close Applications from Visual Basic

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic for Windows, 16-bit only, version 4.0

SUMMARY

Periodically it may be necessary for a programmer to close down another application from Visual Basic code. For example, your application might conflict with some other known utility, so you need to close the conflicting utility so your application can work correctly. The step-by- step example in this article shows how to do it using the Windows API.

MORE INFORMATION

Step-by-Step Example

1. Start a new Visual Basic project. Form1 is created by default.

2. Add a command button (Command1) to Form1.

3. Add the following code to the General Declarations section of Form1:

   Option Explicit

      Private Declare Function FindWindow Lib "User" (ByVal lpClassName _
         As Any, ByVal lpWindowName As Any) As Integer
      Private Declare Function PostMessage Lib "User" (ByVal hWnd _
         As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, _
         lParam As Any) As Integer
   
      Private Const WM_QUIT = &H12
   
      Private Sub Command1_Click()
        Dim sTitle As String
        Dim iHwnd As Integer
        Dim ihTask As Integer
        Dim iReturn As Integer
        sTitle = "Notepad - (Untitled)"
        iHwnd = FindWindow(0&, sTitle)
        iReturn = PostMessage(iHwnd, WM_QUIT, 0, 0&)
        MsgBox "Notepad has been Closed Down"
      End Sub
   
   

4. Start Notepad by double-clicking the Notepad Icon.

5. Activate Visual Basic, and press F5 to start the project. Click the command button and the instance of Notepad you started should automatically close down. The message box will confirm this.

1. Start a new Visual Basic project. Form1 is created by default.

2. Add a command button (Command1) to Form1.

3. Add the following code to the General Declarations section of Form1:

   Option Explicit

   Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal
   

Private Declare Function PostMessage Lib "user32" Alias "PostMessageA"

Private Sub Command1_Click()
    Dim sTitle As String
     Dim iHwnd As Long
     Dim ihTask As Long
     Dim iReturn As Long
     sTitle = "Untitled - Notepad"
     iHwnd = FindWindow(0&, sTitle)
     iReturn = PostMessage(iHwnd, WM_QUIT, 0&, 0&)
     MsgBox "Notepad has been Closed Down"

End Sub