DataGrid相邻行有相同内容时对指定列合并

/**//// <summary>
/// DataGrid相邻行有相同内容时对指定列合并
/// </summary>
/// <param name="spangrid">格式化的DataGrid的ID</param>
/// <param name="spancell">要合并的列</param>        
/// <param name="spanby">合并所依据数据的列</param>
    public void FormatGrid(DataGrid spangrid,int spancell,int spanby)
    {
      if(spanby<0 || spanby>spangrid.Items.Count)
          return;
          int rowspan = 1;
          for(int i = 1;i<spangrid.Items.Count;i++)
         {
        if(spangrid.Items[i].Cells[spanby].Text == spangrid.Items[i-1].Cells[spanby].Text)
            {
                
               rowspan +=1;
               spangrid.Items[i].Cells[spancell].Visible = false;
               spangrid.Items[i-rowspan+1].Cells[spancell].RowSpan = rowspan;
            }
        else
        {    
           string str = spangrid.Items[i].Cells[spanby].Text;
           string str1 = spangrid.Items[i-1].Cells[spanby].Text;
           rowspan = 1;
        }    
              }
    }