Add project files.

RepositoryPattern/IProductRepository.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace RepositoryPattern
+{
+    public interface IProductRepository
+    {
+        IEnumerable<Product> GetProducts();
+        bool Insert(Product product);
+        bool Update(Product product);
+        bool Delete(string  productId);
+    }
+}