C#编程：实现窗口拖动功能

新建一个类  复制如下代码进去

using System.Text;  
using System.Runtime.InteropServices;  
using System.Windows.Forms;  
namespace BRO  
{  
    class DragControl  
    {  
        //c#拖动无标题窗体  
        [DllImport("user32.dll")]  
       private static extern bool ReleaseCapture();  
       [DllImport("user32.dll")]  
        private static extern bool SendMessage(System.IntPtr hwnd, int wMsg, int wParam, int lParam);  
        private const int WM_SYSCOMMAND = 0x0112;  
        private const int SC_MOVE = 0xF010;  
        private const int HTCAPTION = 0x0002;  
        internal System.Windows.Forms.Control m_DragUI = null;  
        public static void SetDrag(System.Windows.Forms.Control control)  
       {  
            // Control ctlBottomChild=control.find  
            DragControl dragControl = new DragControl();  
            dragControl.m_DragUI = control;  
           dragControl.m_DragUI.MouseDown += new System.Windows.Forms.MouseEventHandler(m_DragUI_MouseDown);  
        }  
        private static void m_DragUI_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)  
        {  
            ReleaseCapture();  
            Control ctlDragControl = sender as Control;  
            if (ctlDragControl is System.Windows.Forms.Form)