c# 字符串转Byte[]，如何将Byte[]插入到Oracle Blob

byte[] xx=Encoding.Default.GetBytes("12121232");

插入数据库

string sqlStr = "update sys_tab t set t.big_logo =:BIG_LOGO,t.small_logo=:SMALL_LOGO where id=:ID";
OracleParameter[] parameterValue = {
new OracleParameter(":BIG_LOGO",OracleType.Blob),
new OracleParameter(":SMALL_LOGO",OracleType.Blob),
new OracleParameter(":ID",OracleType.VarChar,50),
};
parameterValue[0].Value = Encoding.Default.GetBytes("12121232");
parameterValue[1].Value = Encoding.Default.GetBytes("12sad1232");
parameterValue[2].Value = Id;

oracle.Excute(sqlStr, parameterValue);