panel1为Winfrom中的一个panel控件对象。         
            Graphics g = this.panel1.CreateGraphics();
            Color FColor = Color.Blue;
            Color TColor = Color.Green;
            System.Drawing.Brush b = new LinearGradientBrush(this.panel1.ClientRectangle, FColor, TColor, LinearGradientMode.ForwardDiagonal);
            g.FillRectangle(b, this.panel1.ClientRectangle);
            this.panel1.Refresh();
            g.Dispose();