How to use verb GET with WebClient request?

If you use HttpWebRequest instead you would get more control of the call. You can change the REST verb by the Method property (default is GET)

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(HostURI);
request.Method = "GET";
String test = String.Empty;
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
    Stream dataStream = response.GetResponseStream();
    StreamReader reader = new StreamReader(dataStream);
    test = reader.ReadToEnd();
    reader.Close();
    dataStream.Close();
 }
 DeserializeObject(test ...)