DataGridView多维表头的实现方法

         {
             if (this.ColumnHeadersHeightSizeMode != DataGridViewColumnHeadersHeightSizeMode.DisableResizing)
                 this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             int lev=this.Headers.GetHeaderLevels();
             lev=(lev-item.EndY)*_baseColumnHeadHeight;

             SolidBrush backgroundBrush = new SolidBrush(e.CellStyle.BackColor);
             SolidBrush lineBrush = new SolidBrush(this.GridColor);
             Pen linePen = new Pen(lineBrush);
             StringFormat foramt = new StringFormat();
             foramt.Alignment = StringAlignment.Center;
             foramt.LineAlignment = StringAlignment.Center;

             Rectangle headRec = new Rectangle(e.CellBounds.Left, lev, ComputeWidth(item.StartX, item.EndX)-1, ComputeHeight(item.StartY, item.EndY)-1);
             e.Graphics.FillRectangle(backgroundBrush, headRec);
             e.Graphics.DrawLine(linePen, headRec.Left, headRec.Bottom, headRec.Right, headRec.Bottom);
             e.Graphics.DrawLine(linePen, headRec.Right, headRec.Top, headRec.Right, headRec.Bottom);
             e.Graphics.DrawString(item.Content, this.ColumnHeadersDefaultCellStyle.Font, Brushes.Black,headRec, foramt);
         }
     }

     public class HeaderItem
     {
         private int _startX;
         private int _startY;
         private int _endX;
         private int _endY;
         private bool _baseHeader;

         public HeaderItem(int startX, int endX, int startY, int endY, string content)
         {
             this._endX = endX;