DataGridView多维表头的实现方法

         {

         }

         public static HeaderItem CreateBaseHeader(int x,int y,string content)
         {
             HeaderItem header = new HeaderItem();
             header._endX= header._startX = x;
             header._endY= header._startY = y;
             header._baseHeader = true;
             header.Content = content;
             return header;
         }

         public int StartX
         {
             get { return _startX; }
             set
             {
                 if (value > _endX)
                 {
                     _startX = _endX;
                     return;
                 }
                 if (value < 0) _startX = 0;
                 else _startX = value;
             }
         }

         public int StartY
         {
             get { return _startY; }
             set
             {
                 if (_baseHeader)
                 {
                     _startY = 0;