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UnregisterClass function

Applies to: desktop apps only

Unregisters a window class, freeing the memory required for the class.

Syntax

Copy

BOOL WINAPI UnregisterClass(
  __in      LPCTSTR lpClassName,
  __in_opt  HINSTANCE hInstance
);

Parameters

lpClassName [in]

Type: LPCTSTR

A null-terminated string or a class 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 or RegisterClassEx function. System classes, such as dialog box controls, cannot be unregistered. If this parameter is an atom, it must be a class atom created by a previous call to the RegisterClass or RegisterClassEx function. The atom must be in the low-order word of lpClassName; the high-order word must be zero.

hInstance [in, optional]

Type: HINSTANCE

A handle to the instance of the module that created the class.

Return value

Type:

Type: BOOL

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.

Remarks

Before calling this function, an application must destroy all windows created with the specified class.

All window classes that an application registers are unregistered when it terminates.

Class atoms are special atoms returned only by RegisterClass and RegisterClassEx.

No window classes registered by a DLL registers are unregistered when the .dll is unloaded.

Requirements