GraphicDevice.PreferredBackBufferHeight = height;
GraphicDevice.PreferredBackBufferWidth = width;

GraphicsDevice.ApplyChanges();

if (!GraphicsDevice.IsFullScreen)
   GraphicsDevice.ToggleFullScreen();

GraphicsMan = new GraphicsDeviceManager(this);
GraphicsMan.IsFullScreen = false;
GraphicsMan.PreferredBackBufferHeight = 340;
GraphicsMan.PreferredBackBufferWidth = 480;

// Resize the screen to 1024 x 768.
        IntPtr ptr = this.Window.Handle;
        System.Windows.Forms.Form form = (System.Windows.Forms.Form)System.Windows.Forms.Control.FromHandle(ptr);
        form.Size = new System.Drawing.Size(1024, 768);

        graphics.PreferredBackBufferWidth = 1024;
        graphics.PreferredBackBufferHeight = 768;

        graphics.ApplyChanges();