c# – 使用Autofac的.NET Core(MYSQL)通用存储库自动连接

2023年1月6日 416次阅读

我的目标是以下内容.我正在尝试使用以下方法设置新的解决方案：
MySQL,.NET Core,Autofac,EF Core ……利用(通用)存储库模式.

Ultimately I’ll be jumping onto a project with an existing db, thus my aim is to somehow make use of (t4) templates & EF to generate some of the models, then it “should” (famous last words) be as easy as making a repo for each model I need to interact with. (Each repo will just be a small lightweight class inherits the base)

Startup.cs

public class Startup
{
    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
            .AddEnvironmentVariables();
        this.Configuration = builder.Build();
    }

    public IConfigurationRoot Configuration { get; private set; }

    // This method gets called by the runtime. 
    // Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();
        services.
            .AddDbContext<MyContext>(o => o.UseMySQL(
          Configuration.GetConnectionString("MyConnection")));
    }

    public void ConfigureContainer(ContainerBuilder builder)
    {               
        builder.RegisterGeneric(typeof(Repository<>))
            .As(typeof(IRepository<>))
            .InstancePerLifetimeScope();

       // the below works (before adding the repos)
       builder.RegisterAssemblyTypes(AppDomain.CurrentDomain.GetAssemblies())
           .AssignableTo<IService>()
           .AsImplementedInterfaces()
           .InstancePerLifetimeScope();
    }
}

(Generic)Repository.cs

public abstract class Repository<T> : IRepository<T>
    where T : class
{
    private readonly MyContext _context;

    protected Repository(MyContext context)
    {
        _context = context;
    }

    public virtual string Add(T entity)
    {
        if (ValidateAdd(ref entity, out var message))
        {
            _context.Set<T>().Add(entity);
        }

        return message;
    }

    public virtual bool ValidateAdd(ref T entity, out string message)
    {
        message = default(string); 
        return true;
    }

}

存储库的实现：

FooRepository.cs

// public interface IFooRepository: IRepository<Foo>

public class FooRepository: Repository<Foo>, IFooRepository
{
    public FooRepository(MyContext context) : base(context)
    {
    }

    public override bool ValidateAdd(ref Foo entity, out string message)
    {
        // just a hook for pre-insert stuff
        message = "All foos shall fail add";
        return false;
    }
}

然后在服务或控制器中使用,或者你有什么.

FooService.cs

public class FooService: IFooService
{
    private readonly IFooRepository _repository;

    public FooService(IFooRepository repository)
    {
        _repository = repository;
    }

    public void DoSomethingThenAdd()
    {
       // some other business logic specific to this service
        _repository.Add(new Foo()
        {
            Id = 1,
            LastName = "Bar",
            Name = "Foo"
        });
    }
}

问题：

我如何解决所有这些问题……我一直在努力寻找关于MySQL Ef的正确文档,而且我有点觉得那部分是“正常工作”.但正如您在下面的错误日志中所看到的那样,我对存储库的注册搞砸了.

错误：

An error occurred during the activation of a particular registration.

See the inner exception for details.

Registration: Activator = FooService (ReflectionActivator), Services
= [MyApp.Services.Interfaces.IFooService, MyApp.Services.Interfaces.IService], Lifetime =
Autofac.Core.Lifetime.CurrentScopeLifetime, Sharing = Shared,
Ownership = OwnedByLifetimeScope

—> None of the constructors found with ‘Autofac.Core.Activators.Reflection.DefaultConstructorFinder’ on type
‘MyApp.Services.FooService’ can be invoked with the available
services and parameters:

Cannot resolve parameter ‘MyApp.Data.Interfaces.IFooRepository
repository’ of constructor ‘Void
.ctor(MyApp.Data.Interfaces.IFooRepository)’. (See inner exception
for details.)

–> Autofac.Core.DependencyResolutionException: None of the constructors found with
‘Autofac.Core.Activators.Reflection.DefaultConstructorFinder’ on type
‘MyApp.Services.FooService’ can be invoked with the available
services and parameters:

Cannot resolve parameter ‘MyApp.Data.Interfaces.IFooRepository
repository’ of constructor ‘Void
.ctor(MyApp.Data.Interfaces.IFooRepository)’.

最佳答案 以下行将注册Repository< Foo>作为IRepository< Foo>在Autofac中：

builder.RegisterGeneric(typeof(Repository<>))
       .As(typeof(IRepository<>))
       .InstancePerLifetimeScope();

但是IRepository< Foo>不是IFooRepository,FooService需要IFooRepository.这就是为什么Autofac失败并出现以下错误消息：

Cannot resolve parameter ‘MyApp.Data.Interfaces.IFooRepository repository’ of constructor ‘Void .ctor(MyApp.Data.Interfaces.IFooRepository)’.

如果你想保留你的FooRepository和IFooRepository,你必须注册它们：

builder.RegisterType<FooRepository>()
       .As<IFooRepository>()

另一种解决方案是注册IRepository<>的所有实现.

builder.RegisterAssemblyTypes(AppDomain.CurrentDomain.GetAssemblies())
       .AsClosedTypesOf(typeof(IRepository<>))

和FooService应该依赖于Irepository< Foo>而不是IFooRepository

public class FooService: IFooService
{
    private readonly IRepository<Foo> _repository;

    public FooService(IRepository<Foo> repository)
    {
        this._repository = repository;
    }

    // ...
}

当您使用IIS：Assembly scanning – IIS Hosted application时,请小心使用程序集扫描

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