What is the difference between Send Message and Post Message and how these relate to C# ,WPF and Pure windows programming?

c# wpf winapi
user407269 picture user407269 · Jul 31, 2010 · Viewed 52.5k times · Source

What is the difference between Send Message and Post Message ( in terms of pure windows programming) and how these relate to C# ,WPF and Pure windows programming?

I am new to Threading and all related stuff so please excuse me for obvious quesiton . I need to dig out the externals of Threading .. Please let me know the links that help me to build my concept from win32 programming to WPF.

I need to underderstand from Post message to Afx ( call to start a new thread ) to delegate Invok/Begin Invoke to Dispatcher.

Answer

Alex Martelli picture Alex Martelli · Jul 31, 2010

PostMessage (in "pure windows programming", aka win32 API) is asynchronous, i.e., to quote the docs:

Places (posts) a message in the message queue associated with the thread that created the specified window and returns without waiting for the thread to process the message.

To post a message in the message queue associated with a thread, use the PostThreadMessage function.

SendMessage is synchronous, that is, again quoting:

Sends the specified message to a window or windows. The SendMessage function calls the window procedure for the specified window and does not return until the window procedure has processed the message.

To send a message and return immediately, use the SendMessageCallback or SendNotifyMessage function. To post a message to a thread's message queue and return immediately, use the PostMessage or PostThreadMessage function.

A good tutorial on these two functions and their use is here.

The connection to WPF is discussed in this SO question.

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