在ASP.Net Core依赖注入中删除服务 [英] Remove a service in ASP.Net Core Dependency Injection

问题描述

在Asp.Net MVC Core(早期版本，版本1.0或1.1)中，依赖项注入绑定在Startup.cs类中的配置如下:

In an Asp.Net MVC Core (early versions, versions 1.0 or 1.1), dependency injection bindings are configured as follow in the Startup.cs class :

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddScoped<IMyService, MyService>();
        // ...
    }
}

在我的应用程序中，我通常有一个基本的Startup类，其中通用绑定定义为这些行的序列:

In my applications, I usually have a base Startup class, where generic bindings are defined as a sequence of these lines :

public abstract class BaseStartup
{
    public virtual void ConfigureServices(IServiceCollection services)
    {
        services.AddScoped<IMyService1, MyService1>();
        services.AddScoped<IMyService2, MyService2>();
    }
}

然后在我的应用程序中，我继承启动类，并注入其他服务:

Then in my application, I inherit the startup class, and inject other services as well :

public class Startup : BaseStartup
{
    public override void ConfigureServices(IServiceCollection services)
    {
        base.ConfigureServices(services);

        services.AddScoped<IMyService3, MyService3>();
        services.AddScoped<IMyService4, MyService4>();
    }
}

我现在想知道:如何才能覆盖"先前的绑定? 例如，我想删除或修改基类中定义的绑定，例如:

I now wonder : how can I kind of 'override' a previous binding ? I would like, for instance, to either remove, or modify a binding defined in the base class, like :

services.Remove<IMyService1>(); // Doesn't exist
services.AddScoped<IMyService1, MyBetterService1>();

或者只是更新绑定:

services.AddScoped<IMyService1, MyBetterService1>(replacePreviousBinding: true); // Doesn't exist either !

有没有办法做到这一点?或者只是简单地声明一个具有与先前定义的绑定相同接口的新绑定，将覆盖该绑定?

Is there a way to do that ? Or maybe simply declaring a new binding with the same interface as a previously defined binding will override that binding ?

推荐答案

您可以使用普通的集合API删除服务:

You can use normal collection API to remove your services:

services.AddScoped<IService>();

var serviceDescriptor = services.FirstOrDefault(descriptor => descriptor.ServiceType == typeof(IService));
services.Remove(serviceDescriptor);

还可以创建扩展方法来实现相同的目的:

Also you can create extension methods to achieve the same:

public static class ServiceCollectionExtensions
{
    public static IServiceCollection Remove<T>(this IServiceCollection services)
    {
        var serviceDescriptor = services.FirstOrDefault(descriptor => descriptor.ServiceType == typeof(T));
        if (serviceDescriptor != null) services.Remove(serviceDescriptor);

        return services;
    }
}

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