Styjun

I am using C# (ASP.NET). I want to use Google OAuth for accessing the user profile detail in my app. I successfully got the authorization code but having a problem in getting the access token.
I prefer the Google tutorials. In tutorial, I read that I have to send the request and get the response from google. For that, I use System.Net.HttpWebRequest/HttpWebResponse (am I going in the right way). I have used this code...

byte[] buffer = Encoding.ASCII.GetBytes("?code=" + code + "&client_id=xxx&client_secret=xxx&redirect_uri=xxxx&grant_type=authorization_code");
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://accounts.google.com");
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
req.ContentLength = buffer.Length;

Stream strm = req.GetRequestStream();
strm.Write(buffer, 0, buffer.Length);
strm.Close();

HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
Response.Write(((HttpWebResponse)resp).StatusDescription);

But, I got the error:

The remote server returned an error: (405) Method Not Allowed.

Update: Here variable code is authorization code.

I think you are sending the POST request to the wrong endpoint, the correct one is https://accounts.google.com/o/oauth2/token

As I had similar problems in the process of implementing Google auth, I will post the code that works.. The last mentioned problem: error (400) Bad request could be caused by leading '?' in the above code..

 string codeClient = "code="+ t +"&client_id=number.apps.googleusercontent.com&";
 string secretUri = "client_secret=yoursecret&" + "redirect_uri=path&"
 + "grant_type=authorization_code";
 postString = codeClient + secretUri;

 string url = "https://accounts.google.com/o/oauth2/token";

 HttpWebRequest request = (HttpWebRequest) WebRequest.Create(url.ToString());
 request.Method = "POST";
 request.ContentType = "application/x-www-form-urlencoded";

 UTF8Encoding utfenc = new UTF8Encoding();
 byte[] bytes = utfenc.GetBytes(postString);
 Stream os = null;
 try
 
 request.ContentLength = bytes.Length;
 os = request.GetRequestStream();
 os.Write(bytes, 0, bytes.Length);
 
 catch
 

 try
 {
 HttpWebResponse webResponse = (HttpWebResponse) request.GetResponse();
 Stream responseStream = webResponse.GetResponseStream();
 StreamReader responseStreamReader = new StreamReader(responseStream);
 result = responseStreamReader.ReadToEnd();//parse token from result

My code is working, I have done mistakes in above two lines. It should be like this

byte[] buffer = Encoding.ASCII.GetBytes("code=" + code + "&client_id=xxx&client_secret=xxx&redirect_uri=xxxx&grant_type=authorization_code");
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("https://accounts.google.com/o/oauth2/token");

Remaining code is correct.

The original request seems to be somewhat outdated. But I found that the Google's code examples contain lots of "Best Practices" housekeeping code that's hard to separate from the essential operations.

I recently published a document that represents all the REST operations as curl commands. It's hard to be conversant in every language, but curl seems universal. Most people know it- otherwise, it's pretty easy to grasp. In my curl examples, the -d flag indicates a POST operation. Otherwise, the parameters are appended to the URL.

http://www.tqis.com/eloquency/googlecalendar.htm

public string ReceiveTokenGmail(string code, string GoogleWebAppClientID, string GoogleWebAppClientSecret, string RedirectUrl)

 string postString = "code=" + code + "&client_id=" + GoogleWebAppClientID + @"&client_secret=" + GoogleWebAppClientSecret + "&redirect_uri=" + RedirectUrl;

 string url = "https://accounts.google.com/o/oauth2/token";

 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url.ToString());
 request.Method = "POST";
 request.ContentType = "application/x-www-form-urlencoded";

 UTF8Encoding utfenc = new UTF8Encoding();
 byte[] bytes = utfenc.GetBytes(postString);
 Stream os = null;
 try
 
 request.ContentLength = bytes.Length;
 os = request.GetRequestStream();
 os.Write(bytes, 0, bytes.Length);
 
 catch
 
 string result = "";

 HttpWebResponse webResponse = (HttpWebResponse)request.GetResponse();
 Stream responseStream = webResponse.GetResponseStream();
 StreamReader responseStreamReader = new StreamReader(responseStream);
 result = responseStreamReader.ReadToEnd();

 return result;