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up vote 0 down vote favorite

So I'm trying to put together some very simple and elegant code samples to help people use my API. The latest language I'm tackling is C#.

I think the IETF OAuth2.0 standard I read implies the HTTP request Content-Type must be "application/x-www-form-urlencoded". The Django API server I have, currently seems to only support this Content-Type (for the OAuth resource). The other languages POST content this way by default!

After extensive research and several experiments I am wondering if I have missed something fundamental. Surely there would be a helpful library OR technique to create the ...urlencoded string OR at least someone else must have run into this???

I will outline some of the best solution I have so far bellow, but it just seems wrong.

Also from a bunch of internet browsing I figured I would use the HttpClient library. I like the fact that it uses the async model, which perhaps will be more useful for any developers using WPF or XAML or Windows 8 apps. It also works well for Consoles and Forms.

I use the Newtonsoft Json.Net library for serialization. First of all I create a POCO of the authorization strings. Then I serialize it to JSON, then to key/value pairs, then iterate through the key/value pairs catenating with the required '=' and '&' chars, then UTF-8, then escape the spaces etc.

//Setup HTTP request
HttpClient httpRequest = new HttpClient();
httpRequest.DefaultRequestHeaders.Add("Accept", "application/json");
string urlBase = "https://__secret__/api/v1/";
HttpResponseMessage msg = new HttpResponseMessage();

//POST to oauth to get token (must be sent as "application/x-www-form-urlencoded")
OAuthConfig oAuthCredentials = new OAuthConfig { client_id = client_id, client_secret = secret, username = "__secret__", password = "__secret__", grant_type = "__secret__" };
string jsonString = JsonConvert.SerializeObject(oAuthCredentials);  //convert to JSON
Dictionary<string, string> values = JsonConvert.DeserializeObject<Dictionary<string, string>>(jsonString);  //convert to key/value pairs
string urlEncodedData = ConvertToFormUrlEncodedFormat(values);
HttpContent payload = new StringContent(urlEncodedData, Encoding.UTF8, "application/x-www-form-urlencoded");
msg = httpRequest.PostAsync(urlBase + "oauth/access_token/", payload).Result;
string responseBodyAsText = msg.Content.ReadAsStringAsync().Result;
Console.WriteLine(responseBodyAsText);

Other options I could think of were...

Reflection, however digging into reflection in a code sample seems a bit manic.

It turns out that other than the OAuth setup, the rest of the API supports JSON type POSTs. So I guess I could write a function to walk through the oAuthConfig model and catenate a string, since that POCO model is unlikely to change and is the only model which requires urlEncoding that I can anticipate. That would save us from the slightly confusing use of the Dictionary. The use of the dictionary and then iterating is more generic, however perhaps a bit OTT.

I figure most of the time people will be using JSON, so showing how that might happen is useful.

In general it seems quite hard to serialize a POCO model to a string and/or to a urlEncoded string.

Questions

  • does OAuth mandate urlencoded, could you convert server-side?
  • is HttpClient the best choice, does async matter?
  • is there a better simpler way to serialize a POCO to ...form-urlencoded?

Thanks for any useful comments you may have.

share|improve this question

1 Answer 1

up vote 0 down vote 
//I disclaimer everything and note that I haven't re-checked if this posted code works.

using System;
using System.Text;
using System.Collections.Generic;
using Newtonsoft.Json;  //install with Nuget package installer- "json.Net"
using System.Net.Http;  //install with Nuget package installer- "...Web API client libraries"
using System.Net;
using System.IO;
using System.Runtime.Serialization.Json;       //security risk till certificate fixed

namespace CSharpDemoCodeConsole
{
    class Program
    {
        const string api_key = "your_api_key"; //set your api_key here
        const string user_auth = "your_username" + ":" + "your_password"; // set your user credentials here
        const string urlBase = "https://@SECRET.com@/api/v1";

        static void Main(string[] args)
        {
            Console.WriteLine("Making call to webserver asynchronously");
            MakeCallAsynchronously();
            Console.WriteLine("**************************************");

            Console.WriteLine("Making call to webserver synchronously");
            MakeCallSynchronously();
            Console.WriteLine("**************************************");

            Console.WriteLine("Making call to webserver synchronously without Newtonsoft serialization");
            MakeCallSynchronouslyWithoutNewtonSoft();
            Console.WriteLine("Press spacebar to close the application");
            Console.ReadKey();
        }

        private static void MakeCallAsynchronously()
        {
            //Always accept untrusted certificates - don't use in production
            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

            //Setup request
            string authorizeString = Convert.ToBase64String(Encoding.ASCII.GetBytes(user_auth));
            HttpClient httpRequest = new HttpClient();
            httpRequest.DefaultRequestHeaders.Add("Authorization", "Basic " + authorizeString);
            httpRequest.DefaultRequestHeaders.Add("Accept", "application/json");

            //GET from places resource
            try
            {
                var requestTask = httpRequest.GetAsync(urlBase + "places/" + "?api_key=" + api_key,
                System.Net.Http.HttpCompletionOption.ResponseContentRead);

                //Update UI while waiting for task to complete
                while (requestTask.Status != System.Threading.Tasks.TaskStatus.RanToCompletion)
                {
                    Console.Write(".");
                    System.Threading.Thread.Sleep(30);
                }
                if (requestTask.Result.StatusCode != HttpStatusCode.OK)
                {
                    Console.WriteLine("Unexpected response from server: {0}", requestTask.Result);
                    return;
                }
                var places = JsonConvert.DeserializeObject<Page<Place>>(requestTask.Result.Content.ReadAsStringAsync().Result);
                Console.WriteLine("GET places response " + requestTask.Result.Content.ReadAsStringAsync().Result);
            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
                return;
            }

            //POST to places resource
            try
            {
                string jsonString = JsonConvert.SerializeObject(new Place { name = "test place", latitude = 0, longitude = 0 });
                HttpContent payload = new StringContent(jsonString, Encoding.UTF8, "application/json");
                var requestTask = httpRequest.PostAsync(urlBase + "places/" + "?api_key=" + api_key, payload);

                //Update UI while waiting for task to complete
                while (requestTask.Status != System.Threading.Tasks.TaskStatus.RanToCompletion)
                {
                    Console.Write(".");
                    System.Threading.Thread.Sleep(30);
                }
                if (requestTask.Result.StatusCode != HttpStatusCode.Created)
                {
                    Console.WriteLine("Unexpected response from server: {0}", requestTask.Result);
                    return;
                }
                Console.WriteLine("POST places response " + requestTask.Result.Content.ReadAsStringAsync().Result);
            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
                return;
            }
        }

        private static void MakeCallSynchronously()
        {
            //Always accept untrusted certificates - don't use in production
            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

            //Setup Request
            string authorizeString = Convert.ToBase64String(Encoding.ASCII.GetBytes(user_auth));
            var client = new WebClient();
            client.Headers.Add("Authorization", "Basic " + authorizeString);
            client.Headers.Add("Accept", "application/json");

            //GET from places resource
            try
            {
                var responseStream = client.OpenRead(urlBase + "places/" + "?api_key=" + api_key);
                var response = (new StreamReader(responseStream).ReadToEnd());
                var places = JsonConvert.DeserializeObject<Page<Place>>(response);
                Console.WriteLine("GET places response " + response);
            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
            }

            //POST to places resource
            try
            {
                client.Headers.Add("Accept", "application/json");
                client.Headers.Add("Content-Type", "application/json");
                string jsonString = JsonConvert.SerializeObject(new Place { name = "test place", latitude = 0, longitude = 0 });
                client.Encoding = System.Text.Encoding.UTF8;
                string response = client.UploadString(urlBase + "places/" + "?api_key=" + api_key, jsonString);
                Console.WriteLine("POST places response " + response);
            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
                return;
            }
        }

        private static void MakeCallSynchronouslyWithoutNewtonSoft()
        {
            //Always accept untrusted certificates - don't use in production
            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

            //Setup Request
            string authorizeString = Convert.ToBase64String(Encoding.ASCII.GetBytes(user_auth));
            var client = new WebClient();
            client.Headers.Add("Authorization", "Basic " + authorizeString);
            client.Headers.Add("Accept", "application/json");

            //GET from places resource
            try
            {
                var responseStream = client.OpenRead(urlBase + "places/" + "?api_key=" + api_key);
                MemoryStream ms = new MemoryStream();
                responseStream.CopyTo(ms);
                ms.Position = 0;
                var placesDeserializer = new DataContractJsonSerializer(typeof(Page<Place>));
                var places = (Page<Place>)placesDeserializer.ReadObject(ms);
                ms.Position = 0;
                string response = (new StreamReader(ms).ReadToEnd());
                ms.Close();
                Console.WriteLine("GET places response " + response);
            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
                return;
            }

            //POST to places resource
            try
            {
                client.Headers.Add("Accept", "application/json");
                client.Headers.Add("Content-Type", "application/json");
                DataContractJsonSerializer placesSerializer = new DataContractJsonSerializer(typeof(Place));
                Place place = new Place { name = "test place", latitude = 0, longitude = 0 };
                MemoryStream ms = new MemoryStream();
                placesSerializer.WriteObject(ms, place);
                byte[] json = ms.ToArray();
                ms.Close();
                string jsonString = Encoding.UTF8.GetString(json, 0, json.Length);
                client.Encoding = System.Text.Encoding.UTF8;
                string response = client.UploadString(urlBase + "places/" + "?api_key=" + api_key, jsonString);
                Console.WriteLine("POST places response " + response);

            }
            catch (WebException ex)
            {
                Console.WriteLine(ex.ToString());
                return;
            }
        }
    }

    public class Place
    {
        [JsonProperty("url")]
        public string url { get; set; }
        [JsonProperty("name")]
        public string name { get; set; }
        [JsonProperty("latitude")]
        public float latitude { get; set; }
        [JsonProperty("longitude")]
        public float longitude { get; set; }
    }

    public class Page<T>
    {
        [JsonProperty("count")]
        public int count { get; set; }
        [JsonProperty("next")]
        public string next { get; set; }
        [JsonProperty("previous")]
        public string previous { get; set; }
        [JsonProperty("results")]
        public List<T> results { get; set; }
    }
}
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