DataGridView 表头合并(RowSpan)

public class DataGridViewHelper
{
    public DataGridViewHelper(DataGridView gridview)
    {
        gridview.CellPainting += new DataGridViewCellPaintingEventHandler(gridview_CellPainting);
    }

    int top = 0;
    int left = 0;
    int height = 0;
    int width1 = 0;

    public void gridview_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
    {
        #region 重绘datagridview表头
        DataGridView dgv = (DataGridView)(sender);
        if (e.RowIndex != -1) return;
        foreach (TopHeader item in Headers)
        {
            if (e.ColumnIndex >= item.Index && e.ColumnIndex < item.Index + item.Span)
            {
                if (e.ColumnIndex == item.Index)
                {
                    top = e.CellBounds.Top;
                    left = e.CellBounds.Left;
                    height = e.CellBounds.Height;
                }
                int width = 0;//总长度
                for (int i = item.Index; i < item.Span + item.Index; i++)
                {
                    width += dgv.Columns[i].Width;   
                }
                Rectangle rect = new Rectangle(left, top, width, e.CellBounds.Height);
                using (Brush backColorBrush = new SolidBrush(e.CellStyle.BackColor)) //Cell背景颜色
                {
                    //抹去原来的cell背景
                    e.Graphics.FillRectangle(backColorBrush, rect);
                }
                using (Pen gridLinePen = new Pen(dgv.GridColor)) //画笔颜色
                {
                    e.Graphics.DrawLine(gridLinePen, left, top, left + width, top);
                    e.Graphics.DrawLine(gridLinePen, left, top + height / 2, left + width, top + height / 2);
                    e.Graphics.DrawLine(gridLinePen, left, top + height - 1, left + width, top + height - 1); //自定义区域下部横线
                    width1 = 0;
                    e.Graphics.DrawLine(gridLinePen, left - 1, top, left - 1, top + height);
                    for (int i = item.Index; i < item.Span + item.Index; i++)
                    {
                        if (i == 1 || i == 2)
                        {
                            width1 += dgv.Columns[i].Width - 1; //分隔区域首列
                        }
                        else
                        {
                            width1 += dgv.Columns[i].Width; 
                        }
                        e.Graphics.DrawLine(gridLinePen, left + width1 , top + height / 2, left + width1, top + height);
                    }
                    SizeF sf = e.Graphics.MeasureString(item.Text, e.CellStyle.Font);
                    float lstr = (width - sf.Width) / 2;
                    float rstr = (height / 2 - sf.Height) / 2;
                    //画出文本框
                    if (item.Text != "")
                    {
                        e.Graphics.DrawString(item.Text, e.CellStyle.Font,
                                                    new SolidBrush(e.CellStyle.ForeColor),
                                                        left + lstr,
                                                        top + rstr,
                                                        StringFormat.GenericDefault);
                    }
                    width = 0;
                    width1 = 0;
                    for (int i = item.Index; i < item.Span + item.Index; i++)
                    {
                        string columnValue = dgv.Columns[i].HeaderText;
                        width1 = dgv.Columns[i].Width;
                        sf = e.Graphics.MeasureString(columnValue, e.CellStyle.Font);
                        lstr = (width1 - sf.Width) / 2;
                        rstr = (height / 2 - sf.Height) / 2;
                        if (columnValue != "")
                        {
                            e.Graphics.DrawString(columnValue, e.CellStyle.Font,
                                                        new SolidBrush(e.CellStyle.ForeColor),
                                                            left + width + lstr,
                                                            top + height / 2 + rstr,
                                                            StringFormat.GenericDefault);
                        }
                        width += dgv.Columns[i].Width;
                    }
                }
                e.Handled = true;
            }
        }
        #endregion
    }
    private List<TopHeader> _headers = new List<TopHeader>();
    public List<TopHeader> Headers
    {
        get { return _headers; }
    }

    public struct TopHeader
    {
        public TopHeader(int index, int span, string text)
        {
            this.Index = index;
            this.Span = span;
            this.Text = text;
        }
        public int Index;
        public int Span;
        public string Text;
    }
}





调用

DataGridViewHelper helper = new DataGridViewHelper(this.dataGridView2);
helper.Headers.Add(new DataGridViewHelper.TopHeader(1,4,"总计"));

this.dataGridView2.ColumnHeadersHeight = 50; //设置Dgv属性ColumnHeadersHeightSizeMode才会生效