EVE Technology Lab

With the following snippet of C# code which is executed on return from the SSO auth page, I am getting a 400 Bad Request on the last line of displayed code. I've referred to both Single Sign-On and EveLib sources and just don't see anything wrong. Ideas?

public ActionResult EveApiCallback(string code)
{
var query = string.Format("grant_type=authorization_code&code={0}", code);

var req = WebRequest.CreateHttp("https://login.eveonline.com/oauth/token");
req.Method = "POST";
req.Host = "login.eveonline.com";
var bytes = Encoding.ASCII.GetBytes(string.Format("{0}:{1}", ClientId, ClientSecret));
var encoded = Convert.ToBase64String(bytes);
req.Headers.Add("Authorization", "Basic " + encoded);
req.ContentType = "application/x-www-form-urlencoded";
req.ContentLength = query.Length;
using (var writer = new StreamWriter(req.GetRequestStream()))
{
writer.Write(query);
}
var response = req.GetResponse();

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