FAQ Item: How to retrieve a Window Handle in Visual C#.NET?

Question

How to retrieve a Window Handle in Visual C#.NET?

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Answer 1

In many Windows Programming scenarios, we need a Window Handle to perform some tasks, like:

1. Send specified messages to the window,

2. Retrieve/Modify the text of the window,

3. Subclass the window to change its behaviors,

, and so on…

 

If the window is in our .NET Winform application, we can get its handle directly via Control.Handle property,

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.handle(VS.80).aspx

 

If the window is one from another native application, to get its handle, we have to call the Windows API FindWindow or FindWindowEx.

 

FindWindow function is used to retrieve a handle of a top-level window whose class name and window name match the specified strings.

http://msdn.microsoft.com/en-us/library/ms633499(VS.85).aspx

FindWindowEx can be used to find children windows of a specified parent window.

http://msdn.microsoft.com/en-us/library/ms633500(VS.85).aspx

 

The followings are Visual C#.NET PInvoke declarations for the two WinAPIs,

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[DllImport("user32.dll", SetLastError = true)]

static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

 

[DllImport("user32.dll", SetLastError = true)]

static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

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Codes:

IntPtr toplevelWindow = FindWindow(“classname”, ”windowcaption”);

IntPtr childWindow = FindWindowEx(toplevelWindow, new IntPtr(0), “classname”, “windowcaption”);

 

 

Related Threads:

http://social.msdn.microsoft.com/Forums/en-US/csharplanguage/thread/c7c787d0-9426-4b18-b15e-d43821bbb0ea/

http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/4c4f60ce-3573-433d-994e-9c17f95187f0/

http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/d52b9825-dd13-4fd4-bfa8-722114f2ba44

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Please remember to mark the replies as answers if they help and unmark them if they provide no help.