You're calling "response.GetResponse()." It's request.GetResponse().
Update: Based on your comments, I'll propose some new code:
private async void btnRequest_Click(object sender, EventArgs e) // Note: async added
{
string url = "www.google.com";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse response = (HttpWebResponse) await request.GetResponseAsync(); // (note: await added, method call changed to GetResponseAsync()
}
I've updated your code to use the C# 5.0 async and await pattern. This allows you to easily use asynchronous methods while writing code that feels synchronous. In order to do this, I've added the async keyword to the method declaration, prior to the return type (void in this case), and I've added the await keyword prior to calling WebRequest.GetResponseAsync().
To answer your question regarding how to know which library you're using: in this case, you chose a Windows Store app. You should specifically call out what kind of project you're working on - it'll help us nail these kinds of things down faster.