This function retrieves a handle to a display device context (DC) for the client area of the specified window. The display device context can be used in subsequent graphics display interface (GDI) functions to draw in the client area of the window.
The handle the device context for the specified window's client area indicates success. NULL indicates failure.
To get extended error information, call GetLastError.
The GetDC function retrieves a common, class, or private device context depending on the class style specified for the specified window.
For common device contexts, GetDC assigns default attributes to the device context each time it is retrieved.
For class and private device contexts, GetDC leaves the previously assigned attributes unchanged.
After painting with a common device context, the ReleaseDC function must be called to release the device context.
Class and private device contexts do not have to be released.
The number of device contexts is limited only by available memory.