编码格式转换

//utf-8解码（我用在吧url请求的返回xml utf-8格式l解码）

        public string Decode(string value)
        {

            return System.Web.HttpUtility.UrlDecode(value, System.Text.Encoding.UTF8);

        }

  public DataSet ISO8859_GB2312(DataSet ds)
        {
           string xml;
            xml = ds.GetXml();
            ds.Clear();
            //声明字符集  
            System.Text.Encoding iso8859, gb2312;
            //iso8859  
            iso8859 = System.Text.Encoding.GetEncoding("UTF-8");
            //国标2312  
            gb2312 = System.Text.Encoding.GetEncoding("gb2312");
            byte[] bt;
            bt = iso8859.GetBytes(xml);
            xml = gb2312.GetString(bt);
            ds.ReadXml(new System.IO.StringReader(xml));
            return ds;
        }