Iran

    using System.Drawing.Drawing2D;

    private void Form1_Load(object sender, EventArgs e)
        {
            LinearGradientBrush lb = new LinearGradientBrush(this.ClientRectangle, Color.Red, Color.Black, 150);
            ColorBlend cb = new ColorBlend();
            Color[] c = new Color[] { Color.Green, Color.White, Color.Red };
            cb.Colors = c;
            cb.Positions = new float[] { 0.0f, 0.5f, 1f };
            lb.InterpolationColors = cb;
            Bitmap b = new Bitmap(Width, Height);
            Graphics g = Graphics.FromImage(b);
            g.FillRectangle(lb, this.ClientRectangle);
            this.BackgroundImage = b;
        }