c#渐变效果的窗体背景

        public enum WindowStyle : uint
        {
            WS_OVERLAPPED = 0x00000000,
            WS_POPUP = 0x80000000,
            WS_CHILD = 0x40000000,
            WS_MINIMIZE = 0x20000000,
            WS_VISIBLE = 0x10000000,
            WS_DISABLED = 0x08000000,
            WS_CLIPSIBLINGS = 0x04000000,
            WS_CLIPCHILDREN = 0x02000000,
            WS_MAXIMIZE = 0x01000000,
            WS_CAPTION = 0x00C00000,
            WS_BORDER = 0x00800000,
            WS_DLGFRAME = 0x00400000,
            WS_VSCROLL = 0x00200000,
            WS_HSCROLL = 0x00100000,
            WS_SYSMENU = 0x00080000,
            WS_THICKFRAME = 0x00040000,
            WS_GROUP = 0x00020000,
            WS_TABSTOP = 0x00010000,
            WS_MINIMIZEBOX = 0x00020000,
            WS_MAXIMIZEBOX = 0x00010000,
            WS_TILED = WS_OVERLAPPED,
            WS_ICONIC = WS_MINIMIZE,
            WS_SIZEBOX = WS_THICKFRAME,
            WS_TILEDWINDOW = WS_OVERLAPPEDWINDOW,
            WS_OVERLAPPEDWINDOW = (WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU |
                                    WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX),
            WS_POPUPWINDOW = (WS_POPUP | WS_BORDER | WS_SYSMENU),
            WS_CHILDWINDOW = (WS_CHILD)
        }
protected override CreateParams CreateParams
        {
            get
            {
                CreateParams cp = base.CreateParams;
                if (!DesignMode)
                {
                    cp.ExStyle |= (int)WindowStyle.WS_CLIPCHILDREN;
                }
                return cp;
            }
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            DrawFromAlphaMainPart(this, e.Graphics);
        }

        #region Private

        /// <summary>
        /// 绘制窗体主体部分白色透明层
        /// </summary>
        /// <param name="form"></param>
        /// <param name="g"></param>
        public static void DrawFromAlphaMainPart(Form form, Graphics g)
        {
            Color[] colors =
            {
                Color.FromArgb(5, Color.White),
                Color.FromArgb(30, Color.White),
                Color.FromArgb(145, Color.White),
                Color.FromArgb(150, Color.White),
                Color.FromArgb(30, Color.White),
                Color.FromArgb(5, Color.White)
            };
            float[] pos =
            {
                0.0f,
                0.04f,
                0.10f,
                0.90f,
                0.97f,
                1.0f     
            };

            ColorBlend colorBlend = new ColorBlend(6);
            colorBlend.Colors = colors;
            colorBlend.Positions = pos;

            RectangleF destRect = new RectangleF(0, 0, form.Width, form.Height);
            using (LinearGradientBrush lBrush = new LinearGradientBrush(destRect, colors[0], colors[5], LinearGradientMode.Vertical))
            {
                lBrush.InterpolationColors = colorBlend;
                g.FillRectangle(lBrush, destRect);
            }
        }
        #endregion