//   <summary> 
    ///   合并GridView列中相同的行 
    ///   </summary> 
    ///   <param   name="GridView1">GridView对象</param> 
    ///   <param   name="cellNum">需要合并的列</param> 
    public static void GroupRows(GridView GridView1, int cellNum)
    {
        int i = 0, rowSpanNum = 1;
        while (i < GridView1.Rows.Count - 1)
        {
            GridViewRow gvr = GridView1.Rows[i];
            for (++i; i < GridView1.Rows.Count; i++)
            {
                GridViewRow gvrNext = GridView1.Rows[i];
                if (gvr.Cells[cellNum].Text == gvrNext.Cells[cellNum].Text)
                {
                    gvrNext.Cells[cellNum].Visible = false;
                    rowSpanNum++;
                }
                else
                {
                    gvr.Cells[cellNum].RowSpan = rowSpanNum;
                    rowSpanNum = 1;
                    break;
                }

if (i == GridView1.Rows.Count - 1)
                {
                    gvr.Cells[cellNum].RowSpan = rowSpanNum;
                }
            }
        }
    }

///   <summary> 
    ///   根据条件列合并GridView列中相同的行 
    ///   </summary> 
    ///   <param   name="GridView1">GridView对象</param> 
    ///   <param   name="cellNum">需要合并的列</param>
    ///   ///   <param   name="cellNum2">条件列(根据某条件列还合并)</param>
    public static void GroupRows(GridView GridView1, int cellNum, int cellNum2)
    {
        int i = 0, rowSpanNum = 1;
        while (i < GridView1.Rows.Count - 1)
        {
            GridViewRow gvr = GridView1.Rows[i];
            for (++i; i < GridView1.Rows.Count; i++)
            {
                GridViewRow gvrNext = GridView1.Rows[i];
                if (gvr.Cells[cellNum].Text + gvr.Cells[cellNum2].Text == gvrNext.Cells[cellNum].Text + gvrNext.Cells[cellNum2].Text)
                {
                    gvrNext.Cells[cellNum].Visible = false;
                    rowSpanNum++;
                }
                else
                {
                    gvr.Cells[cellNum].RowSpan = rowSpanNum;
                    rowSpanNum = 1;
                    break;
                }

if (i == GridView1.Rows.Count - 1)
                {
                    gvr.Cells[cellNum].RowSpan = rowSpanNum;
                }
            }
        }
    }

第二个方法只是在第一个方法的修改了一点点, 在判断单元格的时候，加上了一个条件列：

if (gvr.Cells[cellNum].Text + gvr.Cells[cellNum2].Text == gvrNext.Cells[cellNum].Text + gvrNext.Cells[cellNum2].Text)。当然，第二个方法还可以扩展，根据多个列的条件来合并。

http://www.cnblogs.com/xjb/archive/2007/12/18/1004203.html