Nothing should ever change screen resolution on the application level, as it can disrupt other application without the user consent. User and only the user should change screen properties, which is done through the control panel.
Instead of trying to do such weird and not legitimate thing, you should develop your application the way they easily adopt any screen size. For some ideas, please see my past answers:
Zom Out malfunctions when Screen resolution changes[
^],
GUI Apperance - C#.Net[
^].
[EDIT]
You can simply maximize the window size or adjust it according to current the screen size in pixels:
http://msdn.microsoft.com/en-us/library/system.windows.window.windowstate%28v=vs.110%29.aspx[
^] (to maximize/restore, etc.),
http://stackoverflow.com/questions/1927540/how-to-get-the-size-of-the-current-screen-in-wpf[
^].
—SA
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