Question

我有以下场景，依赖注入发生在下面给出的类定义之外，因此我无法访问类中的构建器对象。问题是DbContext被映射到两个类，因为我需要使用两个不同的数据库。为了创建SomeClass，需要实例化MyRepository和MyOtherRepository，但要做到这一点需要2个不同的DbContexts。事情失败的地方因为Autofac只采用DbContext映射到MyOtherContext的最后一个映射。非常感谢您解决此问题的任何帮助，谢谢！如果需要更多信息，请告诉我。

public class DependencyResolver : IDependencyResolver
{
   builder.RegisterType<MyContext>().As<DbContext>().InstancePerLifetimeScope();

  builder.RegisterType<MyOtherContext>().As<DbContext>().InstancePerLifetimeScope();

  builder.RegisterType<RepositoryManager.MyRepository>().As<Types.Repository.IMyRepository>().InstancePerDependency();

  builder.RegisterType<RepositoryManager.MyOtherRepository>().As<Types.Repository.IMyOtherRepository>().InstancePerDependency();
}

下面的类定义

public class SomeClass
{
  public SomeClass(IMyRepository myRepository, IMyOtherRepository myOtherRepository)    
  {
      // Code
  }

}

public class MyContext : DbContext
{
   // Code
}

public class MyOtherContext : DbContext
{
   // Code
}

public class MyRepository : IRepository
{
    public MyRepository (DbContext context) : base(context)
    {
        // Code
    }
}

public class MyOtherRepository : IRepository
{
    public MyOtherRepository (DbContext context) : base(context)
    {
        // Code
    }
}

Answer 1

试试这个answer。基本上您正在寻找Autofac的Named and Keyed Services功能。我更喜欢resolving with attributes approach

所以如果你注册这样的上下文：

var builder = new ContainerBuilder();                
        builder
            .RegisterType<MyContext>()
            .As<DbContext>()
            .WithMetadata("EFContext", "My");
        builder
            .RegisterType<MyRepository>()
            .AsImplementedInterfaces();

        builder
            .RegisterType<MyOtherContext>()
            .As<DbContext>()
            .WithMetadata("EFContext", "Other");
        builder
            .RegisterType<MyOtherRepository>()
            .AsImplementedInterfaces();

您应该可以将它们与（非强类型）元数据一起使用：

public class SomeClass
{
    private readonly IMyRepository _myRepository;
    private readonly IMyOtherRepository _myOtherRepository;

    public SomeClass(IMyRepository myRepository, IMyOtherRepository myOtherRepository)
    {
        _myRepository = myRepository;
        _myOtherRepository = myOtherRepository;
    }

    public string SayHello()
    {
        return $"Hello from {_myRepository.ContextName()}  and {_myOtherRepository.ContextName()}";
    }
}

public interface IMyOtherRepository
{
    string ContextName();
}

public interface IMyRepository
{
    string ContextName();
}

public class MyContext : DbContext
{
    // Code
}

public class MyOtherContext : DbContext
{
    // Code
}

public class MyRepository : IMyRepository
{
    private readonly IEnumerable<Meta<DbContext>> _context;

    public MyRepository(IEnumerable<Meta<DbContext>> context)
    {
        _context = context;
        // Code
    }

    public string ContextName() => _context.First(x => x.Metadata["EFContext"].Equals("My")).Value.GetType().Name;
}

public class MyOtherRepository : IMyOtherRepository
{
    private readonly IEnumerable<Meta<DbContext>> _context;

    public MyOtherRepository(IEnumerable<Meta<DbContext>> context)
    {
        this._context = context;
        // Code
    }

    public string ContextName() => _context.First(x => x.Metadata["EFContext"].Equals("Other")).Value.GetType().Name;
}

使用autofac注册多个dbcontext，其中构建器不可用于在注册后解析类

1 个答案: