OracleConnection.Open is throwing ORA-12541 TNS no listener

Question

So I am connecting to an external server through C#. I just installed Oracle 11g client on my machine from here: http://www.oracle.com/technetwork/database/wind

Answer 1

You can do this a couple of ways: Using your TNSNames file the data source should specify the TNSHosts entry name (the bit before the first "=" from the tnsnames.ora), not the host name:

connection.ConnectionString = "Data Source=TestingConnect;Persist Security Info=True;" + "User ID=tesName;Password=test"; 

Or you can put the entire TNS entry in the connection string like so:

connection.ConnectionString = "Data Source=(DESCRIPTION = " +
    "(ADDRESS = (PROTOCOL = TCP)(HOST = TestHostName.us.local)(PORT = 1523))" +
    "(CONNECT_DATA =" + 
    "(SERVER = DEDICATED)" + 
    "(SERVICE_NAME = TEST))" + 
    ");Persist Security Info=True;User ID=tesName;Password=test";