DataTable dt = new DataTable();
        dt.Columns.Add("UserId", typeof(string));
        dt.Columns.Add("UserName", typeof(string));
        for (int i = 0; i < 10; i++)
        {
            dt.Rows.Add(i.ToString(), i.ToString());
        }
        Response.Write("==========修改前=========<br/>");
        foreach (DataRow dr in dt.Rows)
        {
            Response.Write(string.Format("用户ID：{0}---用户名称：{1}<br/>", dr["UserId"], dr["UserName"]));
        }

        dt = dt.AsEnumerable().OrderByDescending(o => o.Field<string>("UserId")).CopyToDataTable();
        Response.Write("==========修改后=========");
        foreach (DataRow dr in dt.Rows)
        {
            Response.Write(string.Format("用户ID：{0}---用户名称：{1}<br/>", dr["UserId"], dr["UserName"]));
        }