How to pass username and password to a web service from within an iPhone app?

Have a look to this code snippet:-

CommonService objcommonService;
NetworkCredential myCredentials = new NetworkCredential("144552", "F@mous123456");
objcommonService.Credentials = myCredentials;

This is a C#.net code. In this snippet “objcommonService” is a object of the webservice “CommonService“. This webservice pre authenticates the user against its supplied credentials.In C#.NET NetworkCredential is a standard class of the .NET .

If I am trying to hit a webservice which requires these credentials in my iPhone app , How should I pass?

Is there any way to do it so that the user of my app will not face any difficulty like “Authentication Failed !!” when he/she uses my app.
The webservice pre authenticates the user.And I need to pass my credentials as my app calls for the service.

How to pass username and password to a web service from within an iPhone app?