The demo code uses the Async features built into .NET 4.5.
Connecting Via Query String Authentication
void TestConnectingViaQueryStringAuthentication()
{
var client = new HttpClient() { BaseAddress = new Uri("https://api.oneguard.net/") };
var userName = "username";
var password = "password";
var response = client.GetAsync(string.Format("api/Test/ShouldJustWork?username={0}&password={1}", userName, password)).Result;
response.EnsureSuccessStatusCode();
var contentResponse = response.Content.ReadAsStringAsync();
Console.WriteLine(contentResponse);
}