Add project files.

ConstructorApp.BusinessLayer/Abstract/IGenericService.cs

@@ -0,0 +1,11 @@
+namespace ConstructorApp.BusinessLayer.Abstract
+{
+    public interface IGenericService<T> where T : class
+    {
+        void TAdd(T entity);
+        void TDelete(T entity);
+        void TUpdate(T entity);
+        T TGetByID(int id);
+        List<T> TGetListAll();
+    }
+}