using GAMongo.Service.DynamicsCRM.Contract;
using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace GAMongo.Service.DynamicsCRM
{
    public static class DynamicsCrmConnector
    {
        public static HttpClient GetHttpClient(string url, string username, string password)
        {
            try
            {
                HttpMessageHandler messageHandler;

                messageHandler = new OAuthMessageHandler(url, new TokenRequest() { Username = username, Password = password }, new HttpClientHandler());

                HttpClient httpClient = new HttpClient(messageHandler)
                {
                    BaseAddress = new Uri(url),
                    Timeout = new TimeSpan(0, 0, 30)  //30 sec
                };
                return httpClient;
            }
            catch (Exception)
            {
                throw;
            }
        }
    }
    class OAuthMessageHandler : DelegatingHandler
    {
        private AuthenticationHeaderValue authHeader;

        public OAuthMessageHandler(string serviceUrl, TokenRequest tokenRequest,
                HttpMessageHandler innerHandler)
            : base(innerHandler)
        {
            var httpContent = new StringContent(JsonConvert.SerializeObject(tokenRequest), Encoding.UTF8, "application/json");

            using (HttpClient client = new HttpClient())
            {
                var response = client.PostAsync(serviceUrl + "/api/token", httpContent).Result;

                if (response.IsSuccessStatusCode)
                {
                    var token = JsonConvert.DeserializeObject<string>(response.Content.ReadAsStringAsync().Result);
                    authHeader = new AuthenticationHeaderValue("Bearer", token);
                }
            }
        }

        protected override Task<HttpResponseMessage> SendAsync(
         HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
        {
            request.Headers.Authorization = authHeader;
            return base.SendAsync(request, cancellationToken);
        }
    }
}


/Usage

public ContactByCardResponse GetContactByCard(ContactByCardRequest request)
        {
            using (HttpClient client = DynamicsCrmConnector.GetHttpClient(_setting.Url, _setting.Username, _setting.Password))
            {
                var httpContent = new StringContent(JsonConvert.SerializeObject(request, Formatting.Indented), Encoding.UTF8, "application/json");
                var response = client.PostAsync(_setting.Url + "/api/Customer/ContactByCard", httpContent).Result;
                return JsonConvert.DeserializeObject<ContactByCardResponse>(response.Content.ReadAsStringAsync().Result);
            }
        }