Throughout all my applications, if I wish to size a window according to the current monitor resolution I use the following:
System.Drawing.Rectangle workingArea = System.Windows.Forms.Screen.FromHandle(new System.Windows.Interop.WindowInteropHelper(App.Current.MainWindow).Handle).WorkingArea;
However, I have one client, who uses multiple monitors, where this is just not working. The resized window is spanning across to a second monitor. Only this one client. I've tested this using multiple monitors and it works fine.
Can anyone please suggest a better/alternative method?