How to get auth code and access code in oauth2 api using c#

Question

I am trying to use sage API which uses oauth2 like facebook and google API. I need to get the authorisation code and exchange it for a access token using Asp.Net C#. My code to manually retrieve the authorisation code is as follows (I am signing in, authorising it, then manually retrieving it from the URL, is this right?):

public ActionResult GetRequest()
        {
            var URL = "https://www.sageone.com/oauth2/auth/central?filter=apiv3.1";
            var urlParameters = "&response_type=code&client_id=_client_id_&redirect_uri=_redirect_uri_&state=d57w5d193";
            return Redirect("https://www.sageone.com/oauth2/auth/central?filter=apiv3.1&response_type=code&client_id=_client_id_&redirect_uri=_redirect_uri_&scope=full_access&state=_state_");
        }

I then manually import the authorisation code into a model and use the following code to post the information to the token URL:

public async Task<string> GetAccess()
        {
            using (var client = new HttpClient())
            {
                client.BaseAddress = new Uri("https://oauth.accounting.sage.com/token");
                var contentType = new MediaTypeWithQualityHeaderValue("application/json");
                client.DefaultRequestHeaders.Accept.Add(contentType);

                AccessTokenSend accessTokenSend = new AccessTokenSend()
                {
                    client_id = "_client_id_",
                    client_secret = "_client_secret",
                    code = "_authorisation_code_from_url",
                    grant_type = "authorization_code",
                    redirect_url = "_redirect_url"
                };
                var json = Newtonsoft.Json.JsonConvert.SerializeObject(accessTokenSend);
                var data = new System.Net.Http.StringContent(json, Encoding.UTF8, "application/json");

                var result = await client.PostAsync("https://oauth.accounting.sage.com/token", data);
                string resultContent = await result.Content.ReadAsStringAsync();

                return resultContent;
            }
        }

This should return the access code but throws an error saying "The auth code you transmitted has an unexpected format". My access token model is as follows:

public class AccessTokenSend
    {
        public string client_id { get; set; }
        public string  client_secret { get; set; }
        public string code { get; set; }
        public string grant_type { get; set; }
        public string redirect_url { get; set; }
    }

Does anyone have any ideas how I am doing this wrong, sage does not provide help for developers beyond postman.

Answer 1

You are sending the data to the token endpoint as JSON. You should be sending them as form data (with content type application/x-www-form-urlencoded ).