Sample for http://stackoverflow.com/questions/39139501/httpclient-post-request-for-webapi-using-asp-net-mvc-application

Sample for stackoverflow.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
  class Program
  {
    public static void Main(string[] args)
    {
      DoWork();
    }

    static async void DoWork()
    {
      string proxyUri = string.Format("{0}:{1}", "proxy.address.com", 3128);

      NetworkCredential proxyCreds = new NetworkCredential(
        "username@domain",
          "password"
      );

      WebProxy proxy = new WebProxy(proxyUri, false)
      {
        UseDefaultCredentials = false,
        Credentials = proxyCreds,
      };

      HttpClientHandler handler = new HttpClientHandler()
      {
        Proxy = proxy,
        PreAuthenticate = true,
        UseDefaultCredentials = true,
      };

      using (var client = new HttpClient(handler))
      {
        try
        {
          const string baseUri = "https://energydevdealswebservices20160719041846.azurewebsites.net/";
          client.BaseAddress = new Uri(baseUri);

          var content = new FormUrlEncodedContent(new[]
          {
            new KeyValuePair<string, string>("deadId", "3"),
            new KeyValuePair<string, string>("flagValueToSet", "true")
          });


          // var response = client.PostAsync("https://energydevdealswebservices20160719041846.azurewebsites.net/Deals/SetDealFlag?dealId=3&flagValueToSet=true", content); // response.Result.IsSuccessStatusCode == true
          var response = client.PostAsync("https://energydevdealswebservices20160719041846.azurewebsites.net/Deals/SetDealFlag", content); // response.Result.IsSuccessStatusCode == false
          response.Wait();
          if (response.Result.IsSuccessStatusCode)
          {
            return;
          }
        }
        catch (Exception ex)
        {
          Console.WriteLine(ex.Message);
          throw;
        }
      }
    }
  }
}