Remote Server Connections from ASP.NET XML Web Service

I am attempting to make a webservice full of tools to help people with a game called Runescape.

I am really confused as to how I would connect to hiscore.web.runescape.com in an ASP.NET Web Service, and be able to send a GET request for a page with query strings.

I am going to have the user input into a field in which is labeled username, and I want to be able to connect to hiscore.web.runescape.com and then use this request:

GET /aff/runescape/hiscorepersonal.cgi?username=usernamewillbehere&category=0 HTTP/1.1

How would I go about connecting to the server and relaying this request to the server, in order to recieve the HTML back?