读取oracle blob字符串

OleDbConnectioncon=newOleDbConnection(cnnstr);
try
{
con.Open();
}
catch
{}
OleDbCommandcmd=newOleDbCommand(strSQL,con);
System.Data.OleDb.OleDbDataReaderdr=cmd.ExecuteReader();
while(dr.Read())
 
{
stringdd=dr["gggg"].ToString();
byte[]ooo=(byte[])dr["hhhh"];
stringstr;
str=System.Text.Encoding.Unicode.GetString(ooo);
this.textBox1.Text=str;
 
}
}
 
 
 //向数据库中写入
        private void button1_Click(object sender, EventArgs e)
        {
            oracleConnection1.Open();
          
            OracleCommand cmd = new OracleCommand("UPDATE TEST SET F2 =:blob where F1=:sn ", oracleConnection1);
           
            cmd.Parameters.Add(new OracleParameter("blob",OracleType.Blob));
              cmd.Parameters.Add(new OracleParameter("sn",OracleType.Int32));
             FileInfo fi = new FileInfo("c:\\dos.doc");
             FileStream fs = fi.OpenRead();
             byte[] MyData = new byte[fs.Length];
             fs.Read(MyData, 0, System.Convert.ToInt32(fs.Length));
             fs.Close();
            cmd.Parameters["blob"].Value = MyData;
            cmd.Parameters["sn"].Value = 1;
&nbs