DataGridView表头合并(ColumnSpan)

/// <summary>
/// 多维表头
/// </summary>
public class DgvHelper
{
   public DgvHelper(DataGridView gridview)
   {
      gridview.RowPostPaint += new DataGridViewRowPostPaintEventHandler(gridview_RowPostPaint);
   }

   private void gridview_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
   {
      DataGridView dgv = (DataGridView)(sender);

      int width = dgv.Width - dgv.RowHeadersWidth;
      int height = 0;

      for (int i = 0; i < dgv.Rows.Count; i++)
      {
            height += dgv.Rows[i].Height; //单元格总高度
      }

      StringFormat SF = new StringFormat() { Alignment = StringAlignment.Center, LineAlignment = StringAlignment.Center };

      Rectangle rect = new Rectangle(e.RowBounds.Left, e.RowBounds.Left + dgv.ColumnHeadersHeight, dgv.Width - width, height);

      using (Brush backColorBrush = new SolidBrush(Color.White)) //设置单元格背景颜色
      {
            e.Graphics.FillRectangle(backColorBrush, rect);
      }
      using (Pen gridLinePen = new Pen(dgv.GridColor))
      {
            //竖线
            e.Graphics.DrawLine(gridLinePen, dgv.Width - width, dgv.ColumnHeadersHeight, dgv.Width - width, height + dgv.ColumnHeadersHeight);
            //根据行拉伸变化画分割线
            //e.Graphics.DrawLine(gridLinePen, e.RowBounds.Left, (height / dgv.Rows.Count) * 5 + dgv.ColumnHeadersHeight, dgv.Width - width - 2, (height / dgv.Rows.Count) * 5 + dgv.ColumnHeadersHeight);
      }
      foreach (LeftHeader item in LeftHeaders)
      {
            using (Pen gridLinePen = new Pen(dgv.GridColor))
            {
               //分割线
               e.Graphics.DrawLine(gridLinePen, e.RowBounds.Left, (height / dgv.Rows.Count) * (item.Span + item.Index) + dgv.ColumnHeadersHeight, dgv.Width - width - 2, (height / dgv.Rows.Count) * (item.Span + item.Index) + dgv.ColumnHeadersHeight);
               //字符串
               e.Graphics.DrawString(item.Text, e.InheritedRowStyle.Font, new SolidBrush(e.InheritedRowStyle.ForeColor), e.RowBounds.Left + dgv.Width - width - (dgv.Width - width) / 2, dgv.ColumnHeadersHeight + ((height / dgv.Rows.Count) * (item.Span + 2 * item.Index)) / 2, SF);
            }
      }
   }

   private List<LeftHeader> leftHeaders = new List<LeftHeader>();
   public List<LeftHeader> LeftHeaders
   {
      get { return leftHeaders; }
   }
   /// <summary>
   /// 合并行表头结构体
   /// </summary>
   public struct LeftHeader
   {
      public LeftHeader(int index, int span, string text)
      {
            this.Index = index;
            this.Span = span;
            this.Text = text;
      }
      public int Index;
      public int Span;
      public string Text;
   }
}