if (m.Msg == WM_NCLBUTTONDOWN)
            {
                int  isDragFullWindow;

                // 1，查询当前系统“拖动显示窗口内容”设置
                SystemParametersInfo(SPI_GETDRAGFULLWINDOWS,0, out isDragFullWindow,0);

                // 2，如果需要修改设置，则在每次进入WM_NCLBUTTONDOWN默认处理之前修改
                if ( isDragFullWindow == 1)
                {
                    SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, 0, 0, 0);                  
                }

                // 3，to do something
                base.WndProc(ref m);

                // 4，处理完毕后，还原系统设置
                if (isDragFullWindow == 1)
                {
                    SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, 0,  1, 0);
                }      
                
            }

        [DllImport("user32.dll",CharSet = CharSet.Auto)]
        public static extern int SystemParametersInfo(int uAction, int uParam,out  int lpvParam, intfuWinIni);