Screen Resolution Problem In WPF?

Keep in mind that all WPF locations and sizes are floating point with a unit of 1/96 inch. Not pixels. This makes your window designs resolution independent. Doing the math: height = 960 / 96 = 10 inches. With your video adapter set to 120 DPI (120/96 = 125%): 10 * 120 = 1200 pixels. Same for width: 1536 / 96 * 120 = 1920 pixels.

System.Windows.Forms works in units of pixels. You are getting less than 1050 for the height because it subtracts the height of the taskbar. But for WPF you always want to work with 1/96", never pixels.

For an even more robust implementation, you should calculate the DPI factors on your system and work with those factors. A normal DPI value is 96, but some monitors may have different values. Consider that your code may be running on a monitor that has a different DPI value than 96. Consider this code:

    private static void CalculateDpiFactors()
    {
        Window MainWindow = Application.Current.MainWindow;
        PresentationSource MainWindowPresentationSource = PresentationSource.FromVisual(MainWindow);
        Matrix m = MainWindowPresentationSource.CompositionTarget.TransformToDevice;
        thisDpiWidthFactor = m.M11;
        thisDpiHeightFactor = m.M22;
    }

You can then use those ratios to get the final values:

CalculateDpiFactors();
double ScreenHeight = SystemParameters.PrimaryScreenHeight * thisDpiHeightFactor;
double ScreenWidth = SystemParameters.PrimaryScreenWidth * thisDpiWidthFactor;

The values of ScreenHeight and ScreenWidth should then match what you see in your monitor's Properties window.