Async Await非同步調用WebApi

先鋪墊一些基礎知識

//sync method sample
        public static void DownLoadWebPage()
        {
            //TODO  cost 5s           
            Console.WriteLine( "DownLoadWebPage on Thread:{0}", Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(5000);
            Console.WriteLine( "End downloading the page.." );
        }

        public static void LoadDatafromDB()
        {
            //TODO  cost 5s           
            Console.WriteLine( "LoadDataFromDB on Thread:{0}", Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(5000);
            Console.WriteLine( "End loading Data.." );
        }

   public static void OurSyncJob()
        {
            Console.WriteLine( "start doing things sync" );
            DownLoadWebPage();
            LoadDatafromDB();
            //do some other things
            Console.WriteLine( "do some other things" );           
        }

       public static async Task OurAsyncJobTask()
        {
            Console.WriteLine( "start doing things async" );
            var taskA= Task.Run(() => { DownLoadWebPage(); });
            var taskB= Task.Run(() => { LoadDatafromDB(); });
            await Task.WhenAll(taskA,taskB);                  
            Console.WriteLine( "do some other things" );
        }

    public class ProductController : ApiController
    {
        public productRepo repo = new productRepo();
        public IEnumerable< Product> getProducts()
        {
            Thread.Sleep(5000); 
            return repo.GetAll();
        }
    }
    public class WidgetController : ApiController
    {
        public widgetRepo repo = new widgetRepo();
        public IEnumerable< Widget> getWidgets()
        {
            Thread.Sleep(5000);
            return repo.GetAll();
        }
    }

    public static List <Product > TaskGetProduct()
    {
       using( HttpClient client= new HttpClient())
       {
                client.BaseAddress = new Uri( "http://localhost:52593/" );
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add( new MediaTypeWithQualityHeaderValue ("application/json" ));
                string json = client.GetString("api/Product/Products" );
                return JsonConvert.DeserializeObject< List< Product>>(json);
       }
    }

public static async Task< List< Product>> TaskGetProduct()
        {
            using( HttpClient client= new HttpClient())
            {
                client.BaseAddress = new Uri( "http://localhost:52593/" );
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add( new MediaTypeWithQualityHeaderValue ("application/json" ));
                string json = await client.GetStringAsync("api/Product/Products" );
                return JsonConvert.DeserializeObject< List< Product>>(json);
            }
        }

       public static async Task< pwgVM> RunTaskGetAll()
        {
            var task1 = TaskGetItem< Product>();
            var task2 = TaskGetItem< Gizmos>();
            var task3 = TaskGetItem< Widget>();
            await Task.WhenAll(task1,task2,task3);
            pwgVM vm = new pwgVM(task1.Result,task2.Result,task3.Result);
            return vm;
        }