public WebResponse Execute(NetworkCredential Credentials)
 {
       HttpWebRequest webRequest = CreateWebRequest(_url, actionUrl);
       webRequest.AllowAutoRedirect = true;
       webRequest.PreAuthenticate = true;
       webRequest.Credentials = Credentials;

       // Add headers and content into the requestStream

       asyncResult.AsyncWaitHandle.WaitOne();
       return webRequest.EndGetResponse(asyncResult);
}

NetworkCredential credential = new NetworkCredential();
credential.UserName = Name;
credential.Password = PW;
Program.CredCache.Add(new Uri("https://blah.com/"), "Basic", credential);

public WebResponse Execute(NetworkCredential Credentials)
 {
        HttpWebRequest webRequest = CreateWebRequest(_url, actionUrl);
        webRequest.AllowAutoRedirect = true;
        webRequest.PreAuthenticate = true;
        webRequest.Credentials = Program.CredCache;

        // more stuff down here
}