使用Visual Studio连接到数据库

我正在尝试使用C#编码连接到oracle数据库，但它说.没有听众.我没有线索.任何人都可以为我提供一个好的解决方案.我也想看看确切的编码.以下是我的代码

I''m trying to connect to the oracle database using C# coding but it says . no listener.I have no clue.Can any one provide me with a good solution please.I want to see the exact coding too please. The following is my code

string oradb = "Data Source=oradb;User Id=hr;Password=oracle;";
        OracleConnection conn = new OracleConnection(oradb);
        conn.Open();
        string sql = "select VALUE from APPBASE.STAGE_LOCALE where LOCALE_ID = 2";
        OracleCommand cmd = new OracleCommand(sql, conn);
        cmd.CommandType = CommandType.Text;
        OracleDataReader dr = cmd.ExecuteReader(); 
        dr.Read();
        Label1.Text = dr["VALUE"].ToString();

        conn.Close();   
        conn.Dispose();