For V8.0 I was successful by making the connection in the following way:
Hashtable connectionProperties = new Hashtable();
connectionProperties.Add(MQC.TRANSPORT_PROPERTY, MQC.TRANSPORT_MQSERIES_MANAGED);
connectionProperties.Add(MQC.HOST_NAME_PROPERTY, _queueServer);
connectionProperties.Add(MQC.PORT_PROPERTY, _portNumber);
connectionProperties.Add(MQC.CHANNEL_PROPERTY, _channelInfo);
connectionProperties.Add(MQC.USER_ID_PROPERTY, "userid");
connectionProperties.Add(MQC.PASSWORD_PROPERTY, "password");
queueManager = new MQQueueManager(_queueManager, connectionProperties);
See here.
Although for version below 8.0 please see that you will have to use an exit mechanism as for them the client provided id is not used.