Added repo doc.

docs/Index.md

@@ -12,7 +12,19 @@
   * <a href="Module-Development-Basics.md" target="_blank">Basics</a>
   * Plug-In Modules
   * Best Practices
+* Domain Driven Design
+  * Domain Layer
+    * [Entities & Aggregate Roots](Entities.md)
+    * Value Objects
+    * [Repositories](Repositories.md)
+    * Domain Services
+    * Specifications
+    * Domain Events
+  * Application Layer
+    * Application Services
+    * Data Transfer Objects
+    * Unit Of Work
 * Data Access
   * [Entity Framework Core Integration](Entity-Framework-Core.md)
-* Presentation (User Interface)
+* Presentation / User Interface
   * Localization

docs/Repositories.md

@@ -0,0 +1,10 @@
+## Repositories
+
+"*Mediates between the domain and data mapping layers using a collection-like interface for accessing domain objects*" (Martin Fowler).
+
+Repositories, in practice, are used to perform database operations for domain objects (see [Entities](Entities.md)). Generally, a separated repository is used for each **aggregate root** or entity.
+
+### Generic Repositories
+
+ABP can provide a default generic repository for each aggregate root or entity. You can [inject](Dependency-Injection.md) `IRepository<TEntity, TKey>` into your service and perform standard CRUD operations. Example usage:
+

test/Volo.Abp.TestApp/Volo/Abp/TestApp/Domain/Person.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.ObjectModel;
+using Volo.Abp.Application.Services;
 using Volo.Abp.Domain.Entities;
+using Volo.Abp.Domain.Repositories;
 using Volo.Abp.MultiTenancy;
 
 namespace Volo.Abp.TestApp.Domain