OAuth 2.0 In .NET With Instagram API

I am working on consuming the Instagram API and I am stuck at step 2 of their OAuth. I have a code from their redirect back to me, but then they want me to do a post with parameters like below…

curl 
    -F 'client_id=CLIENT-ID' 
    -F 'client_secret=CLIENT-SECRET' 
    -F 'grant_type=authorization_code' 
    -F 'redirect_uri=YOUR-REDIRECT-URI' 
    -F 'code=CODE' 
    https://api.instagram.com/oauth/access_token

I am implementing this as an ASP.NET MVC 3 solution. I tried to implement the post like so…

    WebRequest request = HttpWebRequest.Create("https://api.instagram.com/oauth/access_token");
    request.Method = "POST";
    request.Headers.Add("client_id", "sdlf0982jiejfopijfp92jjiwoijf90");
    request.Headers.Add("client_secret", "39993939393939393939393939393");
    request.Headers.Add("grant_type", "authorization_code");
    request.Headers.Add("redirect_uri", "http://localhost:34962/Home/Auth");
    request.Headers.Add("code", 111111);
    var response = request.GetResponse();
    return View();

This gives me a 400 error saying that “client_id is required”. I have included the client_id, but I’m clearly not implementing this correctly.

What is the “best practice” way to perform the second leg of the OAuth?

Answers:

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Method 1

I got the answer from the above mentioned SO post about adding POST parameters to an HttpWebRequest. Here are the details of my implementation.

NameValueCollection parameters = new NameValueCollection();
parameters.Add("client_id", "3498wjfoi2892jf0j2ij02fjakjf2");
parameters.Add("client_secret", "392621gfdlfj2k2hf7g2lfhj2g");
parameters.Add("grant_type", "authorization_code");
parameters.Add("redirect_uri", "http://localhost:34962/Home/Auth");
parameters.Add("code", code);

WebClient client = new WebClient();
var result = client.UploadValues("https://api.instagram.com/oauth/access_token", parameters);

var response = System.Text.Encoding.Default.GetString(result);

return View("Index", (object)response);

Method 2

I spent a lot of time on my task because i didn’t see response error.

        try
    {
        NameValueCollection parameters = new NameValueCollection();
        parameters.Add("client_id", "638ed32066b04801bd40aa05c1542915");
        parameters.Add("client_secret", "fc67cf3645a648ce82106298010acd65");
        parameters.Add("grant_type", "authorization_code");
        parameters.Add("redirect_uri", "http://localhost:34962/Test/InstagramCallback");
        parameters.Add("code", code);

        WebClient client = new WebClient();
        var result = client.UploadValues("https://api.instagram.com/oauth/access_token", "POST", parameters);

        return Encoding.Default.GetString(result);
    }
    catch (WebException ex)
    {
        StreamReader reader = new StreamReader(ex.Response.GetResponseStream());
        string line;
        StringBuilder result = new StringBuilder();
        while ((line = reader.ReadLine()) != null)
        {
            result.Append(line);
        }
        return result.ToString();
    }

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0