1.设置窗体opacity属性：

2.窗体的BackColor和TransparencyKey属性设置相同的值：

2.加using System.Runtime.InteropServices;引用然后加上以下代码：

[StructLayout(LayoutKind.Sequential)]        public struct MARGINS        {            public int Left;            public int Right;            public int Top;            public int Bottom;        }        [DllImport("dwmapi.dll", PreserveSig = false)]        static extern void DwmExtendFrameIntoClientArea(IntPtr hwnd, ref MARGINS margins);        [DllImport("dwmapi.dll", PreserveSig = false)]        static extern bool DwmIsCompositionEnabled();        protected override void OnLoad(EventArgs e)        {            if (DwmIsCompositionEnabled())            {                MARGINS m = new MARGINS();                m.Right = m.Left = m.Top = this.Width + this.Height;                DwmExtendFrameIntoClientArea(this.Handle, ref m);            }            base.OnLoad(e);        }        protected override void OnPaintBackground(PaintEventArgs e)        {            base.OnPaintBackground(e);            if (DwmIsCompositionEnabled())            {                e.Graphics.Clear(Color.Black);            }        }

 

待续...