[DllImport("user32.dll")]
public static extern bool ReleaseCapture();
[DllImport("user32.dll")]
public static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int IParam);
public const int WM_SYSCOMMAND = 0x0112;
public const int SC_MOVE = 0xF010;
public const int HTCAPTION = 0x0002;
[DllImport("user32")]
private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, IntPtr lParam);
private const int WM_SETREDRAW = 0xB;
private void DoFormMoving()
{
if (this.WindowState == FormWindowState.Normal)
{
ReleaseCapture();
SendMessage(this.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
}
}

1. 第二种：

    protected override void WndProc(ref Message m)
           {
               if (m.Msg == 163 && this.ClientRectangle.Contains(this.PointToClient(new Point(m.LParam.ToInt32()))) && m.WParam.ToInt32() == 2)
                   m.WParam = (IntPtr)1;
               base.WndProc(ref m);
               if (m.Msg == 132 && m.Result.ToInt32() == 1)
                   m.Result = (IntPtr)2;
           }
   

   　　

1. 　第一种：　　　

    public void SetWindowRegion()
           {
               System.Drawing.Drawing2D.GraphicsPath FormPath;
               FormPath = new System.Drawing.Drawing2D.GraphicsPath();
               Rectangle rect = new Rectangle(0, 0, this.Width, this.Height);
               FormPath = GetRoundedRectPath(rect, 10);//10为圆色半径
               this.Region = new Region(FormPath);
           }
   
           private GraphicsPath GetRoundedRectPath(Rectangle rect, int radius)
           {
               int diameter = radius;
               Rectangle arcRect = new Rectangle(rect.Location, new Size(diameter, diameter));
               GraphicsPath path = new GraphicsPath();
   
               path.AddArc(arcRect, 180, 90);//左上角
   
               arcRect.X = rect.Right - diameter;//右上角
               path.AddArc(arcRect, 270, 90);
   
               arcRect.Y = rect.Bottom - diameter;// 右下角
               path.AddArc(arcRect, 0, 90);
   
               arcRect.X = rect.Left;// 左下角
               path.AddArc(arcRect, 90, 90);
               path.CloseFigure();
               return path;
           }
   
    private void frmLogin_Resize(object sender, EventArgs e)
           {
               if (this.WindowState == FormWindowState.Normal)
               {
                   SetWindowRegion();
               }
               else
               {
                   this.Region = null;
               }
           }
   

   　　

   　　

   public const int CS_DropSHADOW = 0x20000;
        public const int GCL_STYLE = (-26);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int SetClassLong(IntPtr hwnd, int nIndex, int dwNewLong);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int GetClassLong(IntPtr hwnd, int nIndex);

 public frmLogin()
        {
            InitializeComponent();
            SetClassLong(this.Handle, GCL_STYLE, GetClassLong(this.Handle, GCL_STYLE) | CS_DropSHADOW); 
        }