Web Application Development Tutorial - Part 7: Authors: Database Integration

Introduction

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

DB Context

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

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

Then locate to the OnModelCreating method in BookStoreDbContext class in the same project and add the following lines to the end of the method:

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

The startup solution is configured to use Entity Framework Core Code First Migrations. Since we've changed the database mapping configuration, we should create a new migration and apply changes to the database.

Open a command-line terminal in the directory of the Acme.BookStore.EntityFrameworkCore project and type the following command:

dotnet ef migrations add Added_Authors

This will add a new migration class to the project:

You can apply changes to the database using the following command, in the same command-line terminal:

dotnet ef database update

If you are using Visual Studio, you may want to use the Add-Migration Added_Authors and Update-Database commands in the Package Manager Console (PMC). In this case, ensure that Acme.BookStore.EntityFrameworkCore is the startup project in Visual Studio and Acme.BookStore.EntityFrameworkCore is the Default Project in PMC.

Implementing the IAuthorRepository

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

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)
    {
        var dbSet = await GetDbSetAsync();
        return await dbSet.FirstOrDefaultAsync(author => author.Name == name);
    }

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

• Inherited from the EfCoreRepository, so it inherits the standard repository method implementations.
• WhereIf is a shortcut extension method of the ABP. 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 NuGet package.

See the EF Core Integration document for more information on the EF Core based repositories.