如何在 System.Web.UI.Page 中解析相同类型的多个依赖项，其中这些依赖项实现通用接口

Question

在 BasePage.cs class 中，我有以下 IIndex 属性，它应该有两个 "or more" INotificationService 实现，可以使用密钥访问。

public class BasePage : Page
{
    public IIndex<string, INotificationService<INotification>> NotificationServices { get; set; }

    public INotificationService<INotification> EmailService
    {
        get
        {
            return NotificationServices["emailService"];
        }
    }
    public INotificationService<INotification> FaxService
    {
        get
        {
            return NotificationServices["faxService"];
        }
    }
}

具体类:

public class FaxNotificationService : INotificationService<FaxNotification>
{
    private IClient _smtpClient;
    public FaxNotificationService(IClient smtpClient)
    {
        _smtpClient = smtpClient;
    }
    public void Send(FaxNotification notification)
    {
        _smtpClient.Send(notification);
    }
}

public class EmailNotificationService : INotificationService<EmailNotification>
{
    private IClient _smtpClient;
    public EmailNotificationService(IClient smtpClient)
    {
        _smtpClient = smtpClient;
    }
    public void Send(EmailNotification notification)
    {
        _smtpClient.Send(notification);
    }
}

在Global.asax.cs

void Application_Start(object sender, EventArgs e)
    {
        var emailSmtp = new SmtpWrapper(new SmtpClient
        {
            ...
        });


        var faxSmtp = new SmtpWrapper(new SmtpClient
        {
           ...
        });

        var builder = new ContainerBuilder();

// before having the generic interface the following commented code worked perfectly fine

        //builder.RegisterType<EmailNotificationService>()
        //        .Named<INotificationService>("emailService")
        //        .WithParameter("smtpClient", emailSmtp);

        //builder.RegisterType<FaxNotificationService>()
        //       .Named<INotificationService>("faxService")
        //       .WithParameter("smtpClient", faxSmtp);

        builder.RegisterType<EmailNotificationService>()
            .Named<INotificationService<INotification>>("emailService")
            .WithParameter("smtpClient", emailSmtp);


        builder.RegisterType<BasePage>().AsSelf();

        var build = builder.Build();
        _containerProvider = new ContainerProvider(build);

        using (var scope = build.BeginLifetimeScope())
        {
            var service = scope.Resolve<BasePage>();
        }
    }

在 Global.asax.cs 中，我尝试以某种方式注册 EmailNotificationService，但出现异常：

类型 'NotificationServices.EmailNotificationService' 无法分配给服务 'emailService (Shared.NotificationServices.Abstractions.INotificationService`1[[Shared.NotificationServices.Abstractions.INotification ...]

现在我知道为什么它不起作用了。因为在 C# 中甚至不可能执行以下操作：

INotificationService<INotification> service = new EmailNotificationService(new SmtpWrapper(new SmtpClient()));

后一行代码将导致编译时错误：

无法将类型 'NotificationServices.EmailNotificationService' 隐式转换为 'Shared.NotificationServices.Abstractions.INotificationService'。存在显式转换（是否缺少转换？）

大家有什么想法:)

Answer 1

它们可能实现了相同的接口，但不一定被同等对待。类型是一个重要的区别因素。 Solving this is an FAQ in the docs.

如何在 System.Web.UI.Page 中解析相同类型的多个依赖项，其中这些依赖项实现通用接口

how to resolve multiple dependencies of the same type in a System.Web.UI.Page where these dependencies implement a generic interface

c#

asp.net

webforms

autofac