C#winform当FormBorderStyle为None，实现窗口四周边框阴影

当FormBorderStyle为None，可以自定义窗口标题栏。但是窗口四周没有阴影看着难受。

问题：如何给窗口四周添加阴影？

解答：将下面代码块代码添加到你想要添加窗口的代码里面。就可以了。

   public partial class form1: Form{
     [DllImport("Gdi32.dll", EntryPoint = "CreateRoundRectRgn")]
        private static extern IntPtr CreateRoundRectRgn
   (
       int nLeftRect, // x-coordinate of upper-left corner
       int nTopRect, // y-coordinate of upper-left corner
       int nRightRect, // x-coordinate of lower-right corner
       int nBottomRect, // y-coordinate of lower-right corner
       int nWidthEllipse, // height of ellipse
       int nHeightEllipse // width of ellipse
    );
 
        [DllImport("dwmapi.dll")]
        public static extern int DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS pMarInset);
 
        [DllImport("dwmapi.dll")]
        public static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);
 
        [DllImport("dwmapi.dll")]
        public static extern int DwmIsCompositionEnabled(ref int pfEnabled);
 
        private bool m_aeroEnabled;                     // variables for box shadow
        private const int CS_DROPSHADOW = 0x00020000;
        private const int WM_NCPAINT = 0x0085;
        private const int WM_ACTIVATEAPP = 0x001C;
 
        public struct MARGINS                           // struct for box shadow
        {
            public int leftWidth;
            public int rightWidth;
            public int topHeight;
            public int bottomHeight;
        }
 
        private const int WM_NCHITTEST = 0x84;          // variables for dragging the form
        private const int HTCLIENT = 0x1;
        private const int HTCAPTION = 0x2;
 
        protected override CreateParams CreateParams
        {
            get
            {
                m_aeroEnabled = CheckAeroEnabled();
 
                CreateParams cp = base.CreateParams;
                if (!m_aeroEnabled)
                    cp.ClassStyle |= CS_DROPSHADOW;
 
                return cp;
            }
        }
 
        private bool CheckAeroEnabled()
        {
            if (Environment.OSVersion.Version.Major >= 6)
            {
                int enabled = 0;
                DwmIsCompositionEnabled(ref enabled);
                return (enabled == 1) ? true : false;
            }
            return false;
        }
 
        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_NCPAINT:                        // box shadow
                    if (m_aeroEnabled)
                    {
                        var v = 2;
                        DwmSetWindowAttribute(this.Handle, 2, ref v, 4);
                        MARGINS margins = new MARGINS()
                        {
                            bottomHeight = 1,
                            leftWidth = 1,
                            rightWidth = 1,
                            topHeight = 1
                        };
                        DwmExtendFrameIntoClientArea(this.Handle, ref margins);
 
                    }
                    break;
                default:
                    break;
            }
            base.WndProc(ref m);
 
            if (m.Msg == WM_NCHITTEST && (int)m.Result == HTCLIENT)     // drag the form
                m.Result = (IntPtr)HTCAPTION;
 
        }
   public form1()        {            InitializeComponent();        }}