Namespace for Credentials

I wanted to write credential for web services like this

private Credentials credentials;

But i am getting error to this line that The type or namespace n开发者_如何学Pythoname 'Credentials' could not be found (are you missing a using directive or an assembly reference?)

Calling Web Service using ASP.NET

I suspect it's in the ExtentrixWS namespace - which means you need the ExtentrixWS library. But are you actually consuming an ExtentrixWS web service?