Hi Ali,
If you want to execute or interact with the Revit API from WPF or even simple windows form, then I will suggest two ways to do that,
the first way:
is to make your Revit API interacting functions in your form class and make it take an instance of (ExternalCommandData) class then from it you can get the doc and uidoc objects that you will use in your function,
so when you construct the window/form instance inside the IexternalCommand execute method you have to pass the ExternalCommandData to the form constructor, then you can execute your created function from your form/WPF when a button pressed.
the second way (Recommmended) :
is using the IExternalEventHandler interface which also contains an execute function ,
and from it you can make in ExternalEvent then you can .Rise(); this event from your form/WPF once you passed the ExternalEvent instance to the form constructor
you can check this BuildingCoder link for a detailed impelementation
Good luck,
