Problems with PrimaryScreen.Size

It could be your Dpi setting in windows set above 100%

Try using this method, this will scale the resolution to the current system Dpi settings

Winforms:

private Size GetDpiSafeResolution()
{
    using (Graphics graphics = this.CreateGraphics())
    {
        return new Size((Screen.PrimaryScreen.Bounds.Width * (int)graphics.DpiX) / 96
          , (Screen.PrimaryScreen.Bounds.Height * (int)graphics.DpiY) / 96);
    }
}

WPF:

private Size GetDpiSafeResolution()
{
    PresentationSource _presentationSource = PresentationSource.FromVisual(Application.Current.MainWindow);
    Matrix matix = _presentationSource.CompositionTarget.TransformToDevice;
    return new System.Windows.Size(
        System.Windows.SystemParameters.PrimaryScreenWidth * matix.M22,
        System.Windows.SystemParameters.PrimaryScreenHeight * matix.M11);
}

Note: Make sure your MainWindow is loaded before running this code

I don't feel this is a duplicate question, but the answer is the same as on another thread: https://stackoverflow.com/a/13228495/353147 As the question isn't about blurry fonts but why Screen.PrimaryScreen.Bounds.Size returns faulty information. It could help others.

I did run into an error message, that mscorlib threw an null error. From this thread http://forums.asp.net/t/1653876.aspx/1 I was able to discover that unchecking "Enable ClickOnce security settings" fixed it. This seems like a hack, but it works.