DataSet转Json 方法

防止忘记，留着备用   

     /// <summary>
        /// DATASET转JSON
        /// </summary>
        /// <param name="ds"></param>
        /// <returns></returns>
        public static string ToJson(DataSet ds)
        {
            try
            {
                string json = "[";
                foreach (DataRow i in ds.Tables[0].Rows)
                {
                    json += "{";
                    foreach (DataColumn column in ds.Tables[0].Columns)
                    {
                        json += "‘" + column.ColumnName + "‘:";
                        //json += "‘" + column.ColumnName + "‘:‘" + i[column.ColumnName].ToString() + "‘,";
                        if (column.DataType == typeof(DateTime) || column.DataType == typeof(string))
                        {
                            json += "‘" + i[column.ColumnName].ToString() + "‘,";
                        }
                        else
                        {

                            json += "" + i[column.ColumnName].ToString() + ",";
                        }
                    }
                    json = json.Substring(0, json.LastIndexOf(",")) + "},";
                }
                json = json.Substring(0, json.LastIndexOf(","));
                return json + "]";
            }
            catch
            {
                return "没有数据";
            }
        }