Grid View合并单元格

Windows Forms DataGridView 没有提供合并单元格的功能，要实现合并单元格的功能就要在CellPainting事件中使用Graphics.DrawLine和 Graphics.DrawString 自己来“画”。

如下合并第一列，有相同邻居相同值的单元格

  private void dgviewGKSY_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
              // 对第1列相同单元格进行合并
            if (e.ColumnIndex == 0 && e.RowIndex != -1)
            {
                //每列高度
                double eachHeight = dgviewGKSY.Height / dgviewGKSY.Rows.Count;
                using
                    (
                    Brush gridBrush = new SolidBrush(this.dgviewGKSY.GridColor),
                     backColorBrush = new SolidBrush(e.CellStyle.BackColor)
                    )
                {
                    using (Pen gridLinePen = new Pen(gridBrush))
                    {
                        // 清除单元格
                        e.Graphics.FillRectangle(backColorBrush, e.CellBounds);
                        // 画 Grid 边线（仅画单元格的底边线和右边线）
                        //最后一行画底边线
                        if (e.RowIndex == dgviewGKSY.Rows.Count - 1)
                        {
                            e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left,
                            e.CellBounds.Bottom - 1, e.CellBounds.Right - 1,
                            e.CellBounds.Bottom - 1);
                        }
                        // 画右边线，所有行都得画右边线啦
                        e.Graphics.DrawLine(gridLinePen, e.CellBounds.Right - 1,
                           e.CellBounds.Top, e.CellBounds.Right - 1,
                            e.CellBounds.Bottom);
                        //   如果下一行和当前行的数据不同，则在当前的单元格画一条底边线，表示没得合并了
                        if (e.RowIndex < dgviewGKSY.Rows.Count - 1 &&
                        dgviewGKSY.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString() !=
                        e.Value.ToString())
                            e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left,
                            e.CellBounds.Bottom - 1, e.CellBounds.Right - 1,
                            e.CellBounds.Bottom - 1);

                        // 画（填写）单元格内容，相同的内容的单元格只填写第一个
                        if (e.Value != null)
                        {
                           
                            //当该行和下一行的内容相同时就不画，就是说等到该值的最后一个才画
                            if (e.RowIndex > -1 && e.RowIndex                            dgviewGKSY.Rows[e.RowIndex +1].Cells[e.ColumnIndex].Value.ToString() ==
                            e.Value.ToString())
                            {
                                equalCount++;
                            }
                            else
                            {
                               //量出字符的测量值，包括宽度高度
                                SizeF strSize = e.Graphics.MeasureString(dgviewGKSY.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString(), this.dgviewGKSY.Font);
                               
                             
                                //计算一个中间的列，然后在相应位置画出来
                                    //合并高度
                                    double allHeight = equalCount * eachHeight;
                                    //中间位置
                                    double midHeight = allHeight / 2;
                                    int yloc = e.CellBounds.Y - Convert.ToInt32(midHeight);
                                   int yLoc = Convert.ToInt32(yloc+ strSize.Height / 2);
                                  int  xLoc = Convert.ToInt32(e.CellBounds.X + (e.CellBounds.Width - strSize.Width) / 2);
                               
                                e.Graphics.DrawString(dgviewGKSY.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString(), e.CellStyle.Font,
                                    Brushes.Black, xLoc,
                                   yLoc, StringFormat.GenericDefault);
                                equalCount = 0;
                            }

                        }
                        e.Handled = true;

                    }
               
                }
            }
      }

不过此时会有问题：第一次显示是很好的，但当点击了合并单元格时就会出现很怪的事情，字符乱显示在某个位置了，怎么解决？