How to get display resolution (screen size)?

Question

How to get display resolution in XNA/Monogame ? I tried these on my monitor (1600x900):

The below give me 800,600

//1.
GraphicsDevice.DisplayMode.Width
GraphicsDevice.DisplayMode.Height

//2.
GraphicsDeviceManager graphics = new GraphicsDeviceManager(this);
graphics.GraphicsDevice.DisplayMode.Width
graphics.GraphicsDevice.DisplayMode.Height

//3.
GraphicsAdapter.DefaultAdapter.CurrentDisplayMode.Width
GraphicsAdapter.DefaultAdapter.CurrentDisplayMode.Height

//4.
foreach (DisplayMode dm in GraphicsAdapter.DefaultAdapter.SupportedDisplayModes)
{
    Console.WriteLine(dm.Width);
    Console.WriteLine(dm.Height);
}

Answer 1

_ScreenWidth = System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width;
_ScreenHeight = System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height;

extra references: System.Drawing , System.Windows.Forms