datatable转换成json

public static string Dtb2Json(DataTable dtb)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();
            ArrayList dic = new ArrayList();
            foreach (DataRow row in dtb.Rows)
            {
                Dictionary<string, object> drow = new Dictionary<string, object>();
                foreach (DataColumn col in dtb.Columns)
                {
                    drow.Add(col.ColumnName, row[col.ColumnName]);
                }
                dic.Add(drow);
            }
            return jss.Serialize(dic);
        }