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The UnregisterClass function removes a window class, freeing the memory required for the class.

Declare Function UnregisterClass Lib "user32" Alias "UnregisterClassA" (ByVal lpClassName As String, ByVal hInstance As Long) As Long

Operating Systems Supported
Requires Windows NT 3.1 or later; Requires Windows 95 or later


Parameter Information
- lpClassName
Points to a null-terminated string or is an integer atom. If lpClassName is a string, it specifies the window class name. This class name must have been registered by a previous call to the RegisterClass function. System global classes, such as dialog box controls, cannot be unregistered.
If this parameter is an integer atom, it must be a global atom created by a previous call to the RegisterClass function. The atom, a 16-bit value less than 0xC000, must be in the low-order word of lpClassName; the high-order word must be zero.

- hInstance
Identifies the instance of the module that created the class.

Return Values
If the function succeeds, the return value is nonzero.

If the class could not be found or if a window still exists that was created with the class, the return value is zero. To get extended error information, call GetLastError.

Last update: 07 April 2006