newbie need help: asp.net c#

[mylok]

I have an account, I logged in and requested an API Login ID and Key.
Previously I had been using the standard development testing pair, and things worked fine.
But now, my code returns: "The merchant login ID or password is invalid or the account is inactive."

After do some research that error is caused by post URL to wrong URL, and I have to post URL to :

https://secure.authorize.net/gateway/transact.dll.

Here is my question:

My application use their codesample:   gate.Send(apiRequest) ---  AuthorizeNet.dll come with sample.

One of their representative told me their code sample default send to test URL, I assume that is why I got error.

Where I can get the correct .dll which I can Send(apiRequest) to live URL?

If my assume is wrong please correct me. Thank for your help.

[Trevor]

In order to change to a production account, the gate object needs testmode set to false.  You can set this directly on the exising object, or you can add a false as a third variable in the gate constructor.

var gate =newGateway("YOUR_API_LOGIN_ID","YOUR_TRANSACTION_KEY",false);