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PostThreadMessage info  Overview  Group

The PostThreadMessage function places (posts) a message in the message queue of the specified thread and then returns without waiting for the thread to process the message.

BOOL PostThreadMessage(

    DWORD idThread,

// thread identifier

    UINT Msg,

// message to post

    WPARAM wParam,

// first message parameter

    LPARAM lParam 

// second message parameter



Identifies the thread to which the message will be posted.

The function fails if the specified thread does not have a message queue. The system creates a thread's message queue when the thread makes its first call to one of the Win32 USER or GDI functions. For more information, see the Remarks section.

Specifies the type of message to be posted.
Specifies additional message-specific information.
Specifies additional message-specific information.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError. GetLastError returns ERROR_INVALID_THREAD_ID if idThread is not a valid thread identifier, or if the thread specified by idThread does not have a message queue.


The thread to which the message is posted must have created a message queue, or else the call to PostThreadMessage fails. Use one of the following methods to handle this situation:

The thread to which the message is posted retrieves the message by calling the GetMessage or PeekMessage function. The hwnd member of the returned MSG structure is NULL.

See Also

GetCurrentThreadId, GetMessage, GetWindowThreadProcessId, MSG, PeekMessage, PostMessage, Sleep, WaitForSingleObject

file: /Techref/os/win/api/win32/func/src/f68_7.htm, 4KB, , updated: 2000/4/7 12:19, local time: 2022/5/26 01:07,

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