# Web Application Development Tutorial - Part 7: Authors: Database Integration
````json
//[doc-params]
{
    "UI": ["MVC","NG"],
    "DB": ["EF","Mongo"]
}
````
{{
if UI == "MVC"
  UI_Text="mvc"
else if UI == "NG"
  UI_Text="angular"
else
  UI_Text="?"
end
if DB == "EF"
  DB_Text="Entity Framework Core"
else if DB == "Mongo"
  DB_Text="MongoDB"
else
  DB_Text="?"
end
}}

## About This Tutorial

In this tutorial series, you will build an ABP based web application named `Acme.BookStore`. This application is used to manage a list of books and their authors. It is developed using the following technologies:

* **{{DB_Text}}** as the ORM provider. 
* **{{UI_Value}}** as the UI Framework.

This tutorial is organized as the following parts;

- [Part 1: Creating the server side](Part-1.md)
- [Part 2: The book list page](Part-2.md)
- [Part 3: Creating, updating and deleting books](Part-3.md)
- [Part 4: Integration tests](Part-4.md)
- [Part 5: Authorization](Part-5.md)
- [Part 6: Authors: Domain layer](Part-6.md)
- **Part 7: Authors: Database Integration (this part)**
- [Part 8: Authors: Application Layer](Part-8.md)
- [Part 9: Authors: User Interface](Part-9.md)
- [Part 10: Book to Author Relation](Part-10.md)

### Download the Source Code

This tutorials has multiple versions based on your **UI** and **Database** preferences. We've prepared two combinations of the source code to be downloaded:

* [MVC (Razor Pages) UI with EF Core](https://github.com/abpframework/abp-samples/tree/master/BookStore-Mvc-EfCore)
* [Angular UI with MongoDB](https://github.com/abpframework/abp-samples/tree/master/BookStore-Angular-MongoDb)

## Introduction

This part explains how to configure the database integration for the `Author` entity introduced in the previous part.

## DB Context

{{if DB=="EF"}}

Open the `BookStoreDbContext` in the `Acme.BookStore.EntityFrameworkCore` project and add the following `DbSet` property:

````csharp
public DbSet<Author> Authors { get; set; }
````

Then open the `BookStoreDbContextModelCreatingExtensions` class in the same project and add the following lines to the end of the `ConfigureBookStore` method:

````csharp
builder.Entity<Author>(b =>
{
    b.ToTable(BookStoreConsts.DbTablePrefix + "Authors",
        BookStoreConsts.DbSchema);
    
    b.ConfigureByConvention();
    
    b.Property(x => x.Name)
        .IsRequired()
        .HasMaxLength(AuthorConsts.MaxNameLength);

    b.HasIndex(x => x.Name);
});
````

This is just like done for the `Book` entity before, so no need to explain again.

## Create a new Database Migration

Open the **Package Manager Console** on Visual Studio and ensure that the **Default project** is `Acme.BookStore.EntityFrameworkCore.DbMigrations` in the Package Manager Console, as shown on the picture below. Also, set the `Acme.BookStore.Web` as the startup project (right click it on the solution explorer and click to "Set as Startup Project").

Run the following command to create a new database migration:

![bookstore-add-migration-authors](images/bookstore-add-migration-authors.png)

This will create a new migration class. Then run the `Update-Database` command to create the table on the database.

> See the [Microsoft's documentation](https://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/) for more about the EF Core database migrations.

{{else if DB=="Mongo"}}

*TODO: MongoDB part is being prepared...*

{{end}}

## Implementing the IAuthorRepository

{{if DB=="EF"}}

Create a new class, named `EfCoreAuthorRepository` inside the `Acme.BookStore.EntityFrameworkCore` project (in the `Authors` folder) and paste the following code:

````csharp
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Dynamic.Core;
using System.Threading.Tasks;
using Acme.BookStore.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Volo.Abp.Domain.Repositories.EntityFrameworkCore;
using Volo.Abp.EntityFrameworkCore;

namespace Acme.BookStore.Authors
{
    public class EfCoreAuthorRepository
        : EfCoreRepository<BookStoreDbContext, Author, Guid>,
            IAuthorRepository
    {
        public EfCoreAuthorRepository(
            IDbContextProvider<BookStoreDbContext> dbContextProvider)
            : base(dbContextProvider)
        {
        }

        public async Task<Author> FindByNameAsync(string name)
        {
            return await DbSet.FirstOrDefaultAsync(author => author.Name == name);
        }

        public async Task<List<Author>> GetListAsync(
            int skipCount,
            int maxResultCount,
            string sorting,
            string filter = null)
        {
            return await DbSet
                .WhereIf(
                    !filter.IsNullOrWhiteSpace(),
                    author => author.Name.Contains(filter)
                 )
                .OrderBy(sorting)
                .Skip(skipCount)
                .Take(maxResultCount)
                .ToListAsync();
        }
    }
}
````

* Inherited from the `EfCoreAuthorRepository`, so it inherits the standard repository method implementations.
* `WhereIf` is a shortcut extension method of the ABP Framework. It adds the `Where` condition only if the first condition meets (it filters by name, only if the filter was provided). You could do the same yourself, but these type of shortcut methods makes our life easier.
* `sorting` can be a string like `Name`, `Name ASC` or `Name DESC`. It is possible by using the [System.Linq.Dynamic.Core](https://www.nuget.org/packages/System.Linq.Dynamic.Core) NuGet package.

{{else if DB=="Mongo"}}

*TODO: MongoDB part is being prepared...*

{{end}}

## The Next Part

See the [next part](part-8.md) of this tutorial.