配置 Unity 以解析构造函数参数和接口

Question

我有一个 FaxService class，它接受两个构造函数参数。

public FaxService(string phone, IFaxProvider faxProvider)

Unity 如何配置为第一个参数发送字符串，第二个参数发送 IFaxProvider 实例？我意识到我可以注入另一个提供字符串的服务，但我正在寻找一个解决方案，我不必更改 FaxService 构造函数参数。

这是我目前所拥有的...

class Program
{
    static void Main(string[] args)
    {
        var container = new UnityContainer();

        var phone = "214-123-4567";
        container.RegisterType<IFaxProvider, EFaxProvider>();
        container.RegisterType<IFaxService, FaxService>(phone);

        var fax = container.Resolve<IFaxService>();
    }
}

public interface IFaxService { }

public interface IFaxProvider { }

public class FaxService : IFaxService
{
    public FaxService(string phone, IFaxProvider faxProvider) { }
}

public class EFaxProvider : IFaxProvider { }

但它抛出...

Unity.Exceptions.ResolutionFailedException HResult=0x80131500
Message=Resolution of the dependency failed, type = 'ConsoleApp3.IFaxService', name = '(none)'. Exception occurred while: while resolving.

Answer 1

var container = new UnityContainer();
var phone = "214-123-4567";
container.RegisterType<IFaxProvider, EFaxProvider>();
container.RegisterType<IFaxService, FaxService>(new InjectionConstructor(phone, typeof(IFaxProvider)));

var fax = container.Resolve<IFaxService>();

Answer 2

I am looking for a solution where I don't have to change the FaxService constructor parameters.

如果不至少指定所有构造函数参数的类型，Unity 中不会内置任何内容来执行此操作。

var container = new UnityContainer();
var phone = "214-123-4567";
container.RegisterType<IFaxService, FaxService>(new InjectionConstructor(phone, typeof(IFaxProvider)));
container.RegisterType<IFaxProvider, EFaxProvider>();

var fax = container.Resolve<IFaxService>();

每次构造函数更改时，参数列表都需要更改。

解决方法

如果您不想在 FaxService 的构造函数更改时更改您的 DI 注册，请构建一个抽象工厂以将 string/primitive 参数与服务分开。通过工厂的构造函数参数传递服务。通过 Build 方法参数传递字符串和原始参数类型。

public class FaxServiceFactory
{
    private readonly IFaxProvider faxProvider;
    public FaxServiceFactory(IFaxProvider faxProvider)
    {
        this.faxProvider = faxProvider ?? throw new ArgumentNullException(nameof(faxProvider));
    }

    public IFaxService Create(string phone)
    {
        return new FaxService(phone, this.faxProvider);
    }
}

然后像这样注册：

var container = new UnityContainer();

var phone = "214-123-4567";
container.RegisterType<FaxServiceFactory>();
container.RegisterType<IFaxProvider, EFaxProvider>();
container.RegisterInstance<IFaxService>(container.Resolve<FaxServiceFactory>().Create(phone));

var fax = container.Resolve<IFaxService>();

另一种可能性是使用允许您指定部分构造函数参数列表的 DI 容器（Autofac、Ninject、StructureMap 和 Castle Windsor 都开箱即用）。

配置 Unity 以解析构造函数参数和接口

configure Unity to resolve a constructor parameter and interface

.net

c#

inversion-of-control

unity-container

解决方法