Refactoring and Adding Tests (#28)

* Introducing repository and refactoring services.
Changing entities to use int keys everywhere.

* Refactoring application services to live in web project and only reference repositories, not EF contexts.

* Cleaning up implementations

* Moving logic out of CatalogController
Moving entity knowledge out of viewmodels.

* Implementing specification includes better for catalogservice

* Cleaning up and adding specification unit tests

src/Infrastructure/Data/EfRepository.cs

@@ -0,0 +1,59 @@
+using ApplicationCore.Interfaces;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.eShopWeb.ApplicationCore.Entities;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Infrastructure.Data
+{
+    public class EfRepository<T> : IRepository<T> where T : BaseEntity
+    {
+        private readonly CatalogContext _dbContext;
+
+        public EfRepository(CatalogContext dbContext)
+        {
+            _dbContext = dbContext;
+        }
+
+        public T GetById(int id)
+        {
+            return _dbContext.Set<T>().SingleOrDefault(e => e.Id == id);
+        }
+
+        public List<T> List()
+        {
+            return _dbContext.Set<T>().ToList();
+        }
+
+        public List<T> List(ISpecification<T> spec)
+        {
+            var queryableResultWithIncludes = spec.Includes
+                .Aggregate(_dbContext.Set<T>().AsQueryable(), 
+                            (current, include) => current.Include(include));
+            return queryableResultWithIncludes
+                            .Where(spec.Criteria)
+                            .ToList();
+        }
+
+        public T Add(T entity)
+        {
+            _dbContext.Set<T>().Add(entity);
+            _dbContext.SaveChanges();
+
+            return entity;
+        }
+
+        public void Delete(T entity)
+        {
+            _dbContext.Set<T>().Remove(entity);
+            _dbContext.SaveChanges();
+        }
+
+        public void Update(T entity)
+        {
+            _dbContext.Entry(entity).State = EntityState.Modified;
+            _dbContext.SaveChanges();
+        }
+
+    }
+}