Скриншот формы c# winforms

Пример:

        Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
        Graphics graphics = Graphics.FromImage(printscreen as Image);
        graphics.CopyFromScreen(0, 0, 0, 0, printscreen.Size);
        printscreen.Save(@"C:\printscreen.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

В параметры CopyFromScreen вы можете подставить свои координаты.