透明色及渐变色设置

 画窗体背景色

//渐变刷

 LinearGradientBrush myBrush = new LinearGradientBrush(new Rectangle(0,0,this.Width,this.Height), Color.FromArgb(50, Color.Blue), Color.FromArgb(40, Color.Red), LinearGradientMode.BackwardDiagonal);

 e.Graphics.FillRectangle(myBrush,0,0,this.Width,this.Height);

 //(阴影刷)
  HatchBrush myhbrush5 = new HatchBrush(HatchStyle.DashedDownwardDiagonal, Color.DarkOrange, Color.Aquamarine);

//实心刷

SolidBrush myBrush = new SolidBrush(Color.AliceBlue);

渐变色Color.FromArgb(50, Color.Blue)

绘制矩形框及其透明背景色

                //渐变
                LinearGradientBrush myBrush = new LinearGradientBrush(ChangeRect,Color.FromArgb(50, Color.Blue), Color.FromArgb(40, Color.Red), LinearGradientMode.BackwardDiagonal);

       g.FillRectangle(myBrush, ChangeRect.X + 1, ChangeRect.Y + 1, ChangeRect.Width - 1, ChangeRect.Height - 1);