WinForm DataGridView 控件实现二级标题

很久没写了，最近做项目，要用到DataGridView控件，要实现下图类似的二维表头显示数据，之前也没做过，网上查了好多，后面还是自己研究了一下。要实现二维表头，需要重写

 OnCellPainting(DataGridViewCellPaintingEventArgs e)函数，具体内容如下：

     protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
        {
            try
            {
                if (e.RowIndex > -1 && e.ColumnIndex > -1)
                {
                    DrawCell(e);
                }
                else
                {
                    //二维表头
                    if (e.RowIndex == -1)
                    {
                        if (SpanRows.ContainsKey(e.ColumnIndex)) //被合并的列
                        {
                            //画边框
                            Graphics g = e.Graphics;
                            e.Paint(e.CellBounds, DataGridViewPaintParts.Background | DataGridViewPaintParts.Border);
                            int left = e.CellBounds.Left, top = e.CellBounds.Top + 2,
                            right = e.CellBounds.Right, bottom = e.CellBounds.Bottom;
                            switch (SpanRows[e.ColumnIndex].Position)
                            {
                               case 1:
                                    left += 2;
                                    break;
                                case 2:
                                    break;
                                case 3:
                                    right -= 2;
                                    break;
                            }
                            //画上半部分底色
                            g.FillRectangle(new SolidBrush(this._mergecolumnheaderbackcolor), left, top,
                            right - left, (bottom - top) / 2);
                            //画中线
                            g.DrawLine(new Pen(this.GridColor), left, (top + bottom) / 2,
                            right, (top + bottom) / 2);
                            //写小标题
                            StringFormat sf = new StringFormat();
                            sf.Alignment = StringAlignment.Center;
                            sf.LineAlignment = StringAlignment.Center;
                            g.DrawString(e.Value + "", e.CellStyle.Font, Brushes.Black,
                            new Rectangle(left, (top + bottom) / 2, right - left, (bottom - top) / 2), sf);
                            left = this.GetColumnDisplayRectangle(SpanRows[e.ColumnIndex].Left, true).Left - 2;
                            if (left < 0)
                                left = this.GetCellDisplayRectangle(-1, -1, true).Width;
                            right = this.GetColumnDisplayRectangle(SpanRows[e.ColumnIndex].Right, true).Right - 2;
                            if (right < 0)
                                right = this.Width;
                            g.DrawString(SpanRows[e.ColumnIndex].Text, e.CellStyle.Font, Brushes.Black,
                            new Rectangle(left, top, right - left, (bottom - top) / 2), sf);
                            e.Handled = true;
                        }
                    }
                }
                base.OnCellPainting(e);
            }
            catch
            { }
        }

重写该函数还不够，还需要知道要合并的列的信息，代码如下：

  #region 二维表头
        private struct SpanInfo //表头信息
        {
            public SpanInfo(string Text, int Position, int Left, int Right)
            {
                this.Text = Text;
                this.Position = Position;
                this.Left = Left;
                this.Right = Right;
            }
            public string Text; //列主标题
            public int Position; //位置，1:左，2中，3右
            public int Left; //对应左行
            public int Right; //对应右行
        }

        private Dictionary<int, SpanInfo> SpanRows = new Dictionary<int, SpanInfo>();//需要2维表头的列

        /// <summary>
        /// 合并列
        /// </summary>
        /// <param name="ColIndex">列的索引</param>
        /// <param name="ColCount">需要合并的列数</param>
        /// <param name="Text">合并列后的文本</param>
        public void AddSpanHeader(int ColIndex, int ColCount, string Text)
        {
            if (ColCount < 2)
            {
                throw new Exception("行宽应大于等于2，合并1列无意义。");
            }
            //将这些列加入列表
            int Right = ColIndex + ColCount - 1; //同一大标题下的最后一列的索引
            SpanRows[ColIndex] = new SpanInfo(Text, 1, ColIndex, Right); //添加标题下的最左列
            SpanRows[Right] = new SpanInfo(Text, 3, ColIndex, Right); //添加该标题下的最右列
            for (int i = ColIndex + 1; i < Right; i++) //中间的列
            {
                SpanRows[i] = new SpanInfo(Text, 2, ColIndex, Right);
            }
        }