点击窗体任意位置移动窗体:
需要添加命名空间:
using System.Runtime.InteropServices;
protected override void OnMouseDown( MouseEventArgs e )
{
    base.OnMouseDown( e );
    if (e.Button == MouseButtons.Left)  // 按下的是鼠标左键              
    {
        ReleaseCapture();   // 释放捕获                 
        SendMessage(this.Handle, WM_NCLBUTTONDOWN, (IntPtr)HTCAPTION, IntPtr.Zero);    // 拖动窗体              
    }
}