Microsoft KB Archive/161337

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), included with:
 * Microsoft Windows NT, versions 3.51, 4.0

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SUMMARY
On Windows NT 3.51, GetProcessWindowStation and GetThreadDesktop will return NULL handles from a service that has not called any USER or GDI APIs.

MORE INFORMATION
Initially, a service will not have a windowstation and desktop associated with it. In order to associate a windowstation and desktop to the service, the service must call a USER or GDI API that interacts with the service's desktop such as GetDesktopWindow or CreateDC. Once one of these APIs has been called, GetProcessWindowStation and GetThreadDesktop will return valid handles.

On Windows NT 4.0, a service will have a windowstation and desktop associated with it initially so there is no need to call a USER or GDI API to connect the service to the windowstation and desktop.