建立和注册Context

1. 安装包 >>> Infrastructure项目

• Microsoft.EntityFrameworkCore.Design
• Microsoft.EntityFrameworkCore.[Sqlite][SqlServer][MySql]
  dotnet add package Microsoft.EntityFrameworkCore.SqlServer
Install-Package Microsoft.EntityFrameworkCore.SqlServer

2. 建立Context

• Entities >>> Core项目

  public class Post : Entity
    {
        // public int Id { get; set; }
        public string Title { get; set; }
        public string Body { get; set; }
        public string Author { get; set; }
        public DateTime LastModified { get; set; }
    }

• Context:DbContext >>>Infrastructure项目

public class ApplicationContext:DbContext
    {
        public ApplicationContext(DbContextOptions<ApplicationContext> options):base(options)
        {
        }
        public DbSet<Post> Posts { get; set; }
    }

3. Startup里注册Context

 //注册Dbcontxt
 services.AddDbContext<ApplicationContext>(options =>
     {
        //var contectionString = "Data Source = localhost; Database = Blog.db; User = sa; Password = password";
        var contectionString = "Data Source = .;Database = Blog.db;Integrated Security=True";
        options.UseSqlServer(contectionString);
      });

4. 数据库迁移

• 快速调出package manager console Alt + T N O
• add-migration [Name]

• update-database

  
  Migrations

5. 添加种子数据

• Seed.cs

public class Seed
    {
        public static async Task SeedAsync(ApplicationContext applicationContext,
                                  ILoggerFactory loggerFactory, int retry = 0)
        {
            int retryForAvailability = retry;
            try
            {
                // TODO: Only run this if using a real database
                // myContext.Database.Migrate();

                if (!applicationContext.Posts.Any())
                {
                    applicationContext.Posts.AddRange(
                        new List<Post>{
                            new Post{
                                Title = "Post Title 1",
                                Body = "Post Body 1",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 2",
                                Body = "Post Body 2",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 3",
                                Body = "Post Body 3",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 4",
                                Body = "Post Body 4",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 5",
                                Body = "Post Body 5",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 6",
                                Body = "Post Body 6",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 7",
                                Body = "Post Body 7",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            },
                            new Post{
                                Title = "Post Title 8",
                                Body = "Post Body 8",
                                Author = "Dave",
                                LastModified = DateTime.Now
                            }
                        }
                    );
                    await applicationContext.SaveChangesAsync();
                }
            }
            catch (Exception ex)
            {
                if (retryForAvailability < 10)
                {
                    retryForAvailability++;
                    var logger = loggerFactory.CreateLogger<Seed>();
                    logger.LogError(ex.Message);
                    await SeedAsync(applicationContext, loggerFactory, retryForAvailability);
                }
            }
        }
    }

• Program中调用

 public static void Main(string[] args)
        {
            var host = CreateWebHostBuilder(args).Build();

            using (var scope = host.Services.CreateScope())
            {
                var services = scope.ServiceProvider;
                var loggerFactory = services.GetRequiredService<ILoggerFactory>();
                try
                {
                    var applicationContext = services.GetRequiredService<ApplicationContext>();
                    //调用方法创建种子数据
                    Seed.SeedAsync(applicationContext, loggerFactory).Wait();
                }
                catch (Exception e) 
                {
                    var logger = loggerFactory.CreateLogger<Program>();
                    logger.LogError(e, "Error occured seeding the Database.");
                }
            }

            host.Run();
        }

• 添加PostController

  [Route("api/posts")]
    public class PostController : Controller
    {
        private readonly ApplicationContext _applicationContext;

        public PostController(ApplicationContext applicationContext)
        {
            _applicationContext = applicationContext;
        }

        [HttpGet]
        public async Task<IActionResult> Get()
        {
            var posts = await _applicationContext.Posts.ToListAsync();

            return Ok(posts);
        }
    }

• 成功

  
  种子文件成功

Repository 仓储服务

与持久化技术无关(使用其他Drapper等替代EF Core)、易于测试、代码重用
IRepository接口：依赖注入、松耦合、DIP原则、易于测试

DIP

• 注入的是接口，而不是具体的类。如果注入Repository这个类，Controller就依赖了Repository，这样就是高级别模块依赖了低级别模块，违反了DIP原则! 应该都依赖于抽象IRepository接口。

1. IRepository >>> Core.Interface

public interface IPostRepository
    {
        Task<IEnumerable<Post>> GetAllPostsAsync();
    }

2. Repository >>> Infrastructure.Repositories

   public class PostRepository : IPostRepository
    {
  //注入DbContext
        private readonly ApplicationContext _applicationContext;

        public PostRepository(ApplicationContext applicationContext)
        {
            _applicationContext = applicationContext;
        }

        public async Task<IEnumerable<Post>> GetAllPostsAsync()
        {
            return await _applicationContext.Posts.ToListAsync();
        }
    }

3. Startup中注册服务

 //注册仓储服务
  services.AddScoped<IPostRepository, PostRepository>();

• 服务注册生命周期
  • Transient: 每次其它的类请求（不是指HTTP Request）都会创建一个新的实例，它比较适合轻量级的无状态的（Stateless）的service.
  • Scope: 每次HTTP请求会创建一个实例。
  • Singleton: 在第一次请求的时候就会创建一个实例，以后也只有这一个实例; 或者在ConfigureServices这段代码运行的时候创建唯一一个实例。

4. 修改Controller,注入Repository

[Route("api/posts")]
  public class PostController : Controller
  {
      private readonly IPostRepository _postRepository;

      public PostController(IPostRepository postRepository)
      {
          _postRepository = postRepository;
      }
      [HttpGet]
      public async Task<IActionResult> Get()
      {
          var posts = await _postRepository.GetAllPostsAsync();

          return Ok(posts);
      }
  }

Unit of Work 仓储服务

1. IUntiOfWork >>> Core.Interface

public interface IUnitOfWork
{
  Task<bool> SaveAsync();
}

2. UnitOfWork >>> Infrastructure.Database

 public class UnitOfWork : IUnitOfWork
    {
        private readonly ApplicationContext _applicationContext;

        public UnitOfWork(ApplicationContext applicationContext)
        {
            _applicationContext = applicationContext;
        }

        public async Task<bool> SaveAsync()
        {
            return await _applicationContext.SaveChangesAsync() > 0;
        }
    }

3. Startup中注册服务

 //注册仓储服务
  services.AddScoped<IUnitOfWork , UnitOfWork >();

4. Repository添加AddPost方法

public void AddPost(Post post)
{
    _applicationContext.Posts.Add(post);
}

5. 修改controller, 注入IUnitOfWork, Post()方法中调用

 [Route("api/posts")]
    public class PostController : Controller
    {
        private readonly IPostRepository _postRepository;
        private readonly IUnitOfWork _unitOfWork;

        public PostController(
            IPostRepository postRepository,
            IUnitOfWork unitOfWork)
        {
            _postRepository = postRepository;
            _unitOfWork = unitOfWork;
        }

        [HttpGet]
        public async Task<IActionResult> Get()
        {
            var posts = await _postRepository.GetAllPostsAsync();
            return Ok(posts);
        }

        [HttpPost]
        public async Task<IActionResult> Post()
        {
            var newPost = new Post
            {
                Title = "ENFI",
                Author = "ZGX",
                Body = "adskfasdjfladsjfa;ldsfads",
                LastModified = DateTime.Now
            };
            _postRepository.AddPost(newPost);
            await _unitOfWork.SaveAsync();
            return Ok();
        }
    }

Entity约束

1. PostConfiguration.cs >>> Infrastructure.EntityConfiguration

public class PostConfiguration : IEntityTypeConfiguration<Post>
{
      public void Configure(EntityTypeBuilder<Post> builder)
      {
          builder.Property(x => x.Author).IsRequired().HasMaxLength(50);
          builder.Property(x => x.Title).IsRequired().HasMaxLength(100);
          builder.Property(x => x.Body).IsRequired().HasColumnType("nvarchar(max)");
      }
}

2. DbContext中重写OnModel

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
     base.OnModelCreating(modelBuilder);
     modelBuilder.ApplyConfiguration(new PostConfiguration());
 }