add FirstAsync in respository (#370)

* add FirstAsync in respository

* use new FirstOrDefaultAsync() method from repository

src/ApplicationCore/Interfaces/IAsyncRepository.cs

@@ -13,5 +13,7 @@ namespace Microsoft.eShopWeb.ApplicationCore.Interfaces
         Task UpdateAsync(T entity);
         Task DeleteAsync(T entity);
         Task<int> CountAsync(ISpecification<T> spec);
+        Task<T> FirstAsync(ISpecification<T> spec);
+        Task<T> FirstOrDefaultAsync(ISpecification<T> spec);
     }
 }

src/ApplicationCore/Services/BasketService.cs

@@ -39,7 +39,7 @@ namespace Microsoft.eShopWeb.ApplicationCore.Services
         {
             Guard.Against.NullOrEmpty(userName, nameof(userName));
             var basketSpec = new BasketWithItemsSpecification(userName);
-            var basket = (await _basketRepository.ListAsync(basketSpec)).FirstOrDefault();
+            var basket = (await _basketRepository.FirstOrDefaultAsync(basketSpec));
             if (basket == null)
             {
                 _logger.LogInformation($"No basket found for {userName}");
@@ -72,7 +72,7 @@ namespace Microsoft.eShopWeb.ApplicationCore.Services
             Guard.Against.NullOrEmpty(anonymousId, nameof(anonymousId));
             Guard.Against.NullOrEmpty(userName, nameof(userName));
             var basketSpec = new BasketWithItemsSpecification(anonymousId);
-            var basket = (await _basketRepository.ListAsync(basketSpec)).FirstOrDefault();
+            var basket = (await _basketRepository.FirstOrDefaultAsync(basketSpec));
             if (basket == null) return;
             basket.SetNewBuyerId(userName);
             await _basketRepository.UpdateAsync(basket);

src/Infrastructure/Data/EfRepository.cs

@@ -61,6 +61,16 @@ namespace Microsoft.eShopWeb.Infrastructure.Data
             await _dbContext.SaveChangesAsync();
         }
 
+        public async Task<T> FirstAsync(ISpecification<T> spec)
+        {
+            return await ApplySpecification(spec).FirstAsync();
+        }
+
+        public async Task<T> FirstOrDefaultAsync(ISpecification<T> spec)
+        {
+            return await ApplySpecification(spec).FirstOrDefaultAsync();
+        }
+
         private IQueryable<T> ApplySpecification(ISpecification<T> spec)
         {
             return SpecificationEvaluator<T>.GetQuery(_dbContext.Set<T>().AsQueryable(), spec);

src/Web/Services/BasketViewModelService.cs

@@ -5,7 +5,6 @@ using Microsoft.eShopWeb.ApplicationCore.Specifications;
 using Microsoft.eShopWeb.Web.Interfaces;
 using Microsoft.eShopWeb.Web.Pages.Basket;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading.Tasks;
 
 namespace Microsoft.eShopWeb.Web.Services
@@ -28,7 +27,7 @@ namespace Microsoft.eShopWeb.Web.Services
         public async Task<BasketViewModel> GetOrCreateBasketForUser(string userName)
         {
             var basketSpec = new BasketWithItemsSpecification(userName);
-            var basket = (await _basketRepository.ListAsync(basketSpec)).FirstOrDefault();
+            var basket = (await _basketRepository.FirstOrDefaultAsync(basketSpec));
 
             if (basket == null)
             {