参考：http://topic.csdn.net/u/20080330/14/6b26bc14-0932-4016-9704-6f012ef04f66.html

方案1：通过重载消息处理实现。（优点：不用声明api函数。缺点是：窗体上放着Panel等容器就会失效） 

C# code

const int WM_NCHITTEST = 0x0084;

const int HTLEFT = 10;

const int HTCAPTION = 2;

const int HTCLIENT = 1;

protected override void WndProc(ref Message m)

{

base.WndProc(ref m);

switch (m.Msg)

{

case WM_NCHITTEST:

if (m.Result == (IntPtr)HTCLIENT)

m.Result = (IntPtr)HTCAPTION;

break;

}

}

方案2：发送一个拖动的消息（优点是：可以放在任意控件鼠标按下事件中） 

C# code

using System.Runtime.InteropServices;


[DllImport(
"User32.DLL")]

public static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

[DllImport("User32.DLL")]

public static extern bool ReleaseCapture();

public const uint WM_SYSCOMMAND = 0x0112;

public const int SC_MOVE = 61456;

public const int HTCAPTION = 2;private void Form1_MouseDown(object sender, MouseEventArgs e)

{

ReleaseCapture();

SendMessage(Handle, WM_SYSCOMMAND, SC_MOVE | HTCAPTION, 0);

}