Restful-web-services - calling function with parameter

I need to call function from restful web service which have complex parameter class from. How can I call function with parameter? I'm using mvc 3 for my restful web service and application that is calling it. This is code for calling web service's function :

 HttpWebRequest req = (HttpWebRequest)WebRequest.Create(uri);           
HttpWebResponse response = (HttpWebRes开发者_运维知识库ponse)req.GetResponse();

How can I pass parameter to function? Thx