Closing a Windows Application with LabVIEW

In this article, you will learn how to close an application in Windows systems using the Win32 API within LabVIEW. By sending Windows Messages such as WM_CLOSE, you can programmatically control and exit other running applications. This process involves using the Call Library Function Node to interface with the user32.dll.

Follow these steps :

1. Place two Call Library Function Node VIs on the block diagram and select the DLL user32.dll which is found under C:\Windows\SysWOW64.
    
2. Select the function FindWindowA in the first Call Library Function Node and put  these three parameters (the return type is 32-bits integer): 
   • hWnd (32-bits integer)
   • lpszClassName (32-bits integer)
   • lpszWindowName (pointer to a string)
      
3. Select the function SendMessageA in the second Call Library Function Node and put these four parameters (the return type is 32-bits integer too) : 
   • hWnd (32-bits integer)
   • uMsg (32-bits integer )
   • wParam (32-bits integer )
   • lParam (32-bits integer )
      
4. Now you just have to wire a 0 constant to the lpszClassName, and the name of the application you want to close to lpszWindowName of the FindWindowA function.
   
   
   • Wire the return type of the FindWindowA function to the hWnd input of the SendMessageA function and wire a value of 16 in decimal to the uMsg parameters and a zero constant to the last two parameters wParam and lParam.
   • To use the code, type the name of the application you want to close into the Window Name control. For example, to close a Microsoft PowerPoint project, enter Presentation1 - PowerPoint. Check that the name is entered exactly as it appears in the window title to ensure that the application closes correctly.
     
     

Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW diagram.