.net操作mysql中文字符乱码的问题

//写入数据库时进行转换
        public string GB2312_ISO8859(string write)
        {
            //声明字符集
            System.Text.Encoding iso8859, gb2312;
            //iso8859
            iso8859 = System.Text.Encoding.GetEncoding("iso8859-1");
            //国标2312
            gb2312 = System.Text.Encoding.GetEncoding("gb2312");
            byte[] gb;
            gb = gb2312.GetBytes(write);
            //返回转换后的字符
            return iso8859.GetString(gb);
        }

        //读出时进行转换
        public string ISO8859_GB2312(string read)
        {
            //声明字符集
            System.Text.Encoding iso8859, gb2312;
            //iso8859
            iso8859 = System.Text.Encoding.GetEncoding("iso8859-1");
            //国标2312
            gb2312 = System.Text.Encoding.GetEncoding("gb2312");
            byte[] iso;
            iso = iso8859.GetBytes(read);
            //返回转换后的字符
            return gb2312.GetString(iso);
        }

        //批量数据转换
        //其实就是将dataset的内容读出到xml文件，然后再输出
        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("iso8859-1");
            //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;
        }