GridView单元格合并问题 错误提示：必须在顶级静态类中定义扩展方法；GridViewExtensions 为嵌套类
 public static class GridViewExtensions
    {
public static GridView RowSpan(this GridView gridView, object field)
        {
Dictionary<string, string> rowDictionary = ObjectLoadDictionary(field);
            int columnIndex = int.Parse(rowDictionary["ColumnIndex"]);
            string columnName = rowDictionary["ColumnControlID"];
            string propertyName = rowDictionary["PropertyName"];
            string columns = rowDictionary["Columns"];
            for (var i = 0; i < gridView.Rows.Count; i++)
            {

                int rowSpanCount = 1;
                for (int j = i + 1; j < gridView.Rows.Count; j++)
                {
                    //绑定行合并处理
                    if (string.IsNullOrEmpty(columnName))
                    {
                        //比较2行的值是否相同
                        if (gridView.Rows[i].Cells[columnIndex].Text == gridView.Rows[j].Cells[columnIndex].Text)
                        {
                            //合并行的数量+1
                            rowSpanCount++;
                            //隐藏相同的行
                            gridView.Rows[j].Cells[columnIndex].Visible = false;
                            if (!string.IsNullOrEmpty(columns))
                            {