超过4000长度的字符串如何添加到oracle数据库中

string conn = "Data Source=客户端指定连接字符串;User ID=user;Password=mima"; 
OracleConnection Con = new System.Data.OracleClient.OracleConnection(conn); 
Con.Open(); 
string cmdText = "INSERT INTO GWEXPOINTLIST(id, name, content) VALUES(1, 'name', :clob)"; 
OracleCommand cmd = new OracleCommand(cmdText, Con); 
OracleParameter op = new OracleParameter("clob", OracleType.Clob); 
op.Value = "超过4000字符的超常字符串"; 
cmd.Parameters.Add(op); 
cmd.ExecuteNonQuery(); 
Con.Close();