CORS issue in .Net Framework 4.5 with Angular 6

Question

I have created API in .Net Framework4.5 and It's working fine in Postman but When i implenting with Angular7 then we didn't get Requested Parameters like(Username and Pass) in API. 

I have already tried these steps:

I have already istalled this packege Microsoft.AspNet.WebApi.Cors

DemoController.cs

using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web;
using System.Web.Http;
using System.Web.Http.Cors;
using System.Web.Http.Description;
using TestData.Models;

namespace TestData.Controllers
{


    public class DemoController : ApiController
    {
        [HttpPost]
        [Route("api/Demo/Login")]
        public IHttpActionResult Login(HttpRequestMessage request)
        {
            string username = HttpContext.Current.Request.Form["Username"]; // getting Null
            string pass = HttpContext.Current.Request.Form["Pass"]; // getting Null
            return Ok('Username: ' +username + 'Password :' +pass);
        }
    }
}

WebApiConfig.cs 

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Http;
using System.Web.Http.Cors;

namespace TestData
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
            EnableCorsAttribute cors = new EnableCorsAttribute("*", "*", "*");
            config.EnableCors(cors);
        }
    }
}

I am using some code of Angular

auth.service.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class AuthService {

  apiUrl : any = 'http://mydomain/api';

  constructor(private http : HttpClient) { }

  GetHttpHeaders() : HttpHeaders{
    const headers = new HttpHeaders().set('Content-Type', 'application/json');
    return headers;
  }

  loginUser(){
    var data = JSON.stringify({
      "Username" : '3333',
      "Pass" : '123456'
    })
    return this.http.post(this.apiUrl+'/Demo/Login', data, { headers : this.GetHttpHeaders() }).subscribe((results) => {
      console.log(results);
    });
  }
}