如何让ASP.NET Core中ServiceCollectionExtensions的AddLogger方法更通用

我有一个包含AddLogger方法的ServiceCollectionExtensions类，目前运行正常，但想让它更具泛型性。比如我有类A依赖类B，类B依赖ILogger<B>，现在通过InitServices配置DI依赖项是可行的，但这种方式很脆弱——如果类A的实现变更，开始依赖其他服务，InitServices也得跟着更新。

现有代码 #

TestBase类 #

public abstract class IntegrationTestBase<TService, TImplementation>
where TService : class
where TImplementation : class, TService
{
    protected TService Sut(Action<IServiceCollection>? configureService = default)
    {
        var services = new ServiceCollection();
        services.AddLogger<TImplementation>();
        services.AddSut<TService, TImplementation>();

        configureService?.Invoke(services);

        return services.BuildServiceProvider().GetRequiredService<TService>();
    }
}

ServiceCollectionExtensions类 #

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddLogger<TCategoryName>(this IServiceCollection services) where TCategoryName : class
    {
        services.AddSingleton(Mock.Of<ILogger<TCategoryName>>());
        return services;
    } 
}

测试类 #

[TestMethod]
public void SessionID()
{
    // Arrange
    var swa = Sut(services => InitServices(services));
}

private static void InitServices(IServiceCollection services, bool refreshTokenGrantEnabled = false, bool passwordGrantEnabled = false, bool stsEnabled = true)
{
     services
         .AddSingleton<B>()
         .AddLogger<B>();
}

优化方案 #

1. 注册通用Mock Logger，自动适配所有类型 #

不用再为每个类型手动调用AddLogger<T>，直接注册一个通用的ILogger<T>实现，让DI自动为任意类型提供Logger实例：

修改ServiceCollectionExtensions：

public static class ServiceCollectionExtensions
{
    // 一次性注册通用Mock Logger，覆盖所有ILogger<T>需求
    public static IServiceCollection AddMockLogger(this IServiceCollection services)
    {
        services.AddSingleton(typeof(ILogger<>), typeof(MockLogger<>));
        return services;
    }

    // 通用Mock Logger实现，可按需添加日志逻辑
    private class MockLogger<T> : ILogger<T>
    {
        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;
        public bool IsEnabled(LogLevel logLevel) => true;
        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
        {
            // 可选：在这里输出测试日志，或者留空不处理
        }
    }
}

更新TestBase，只需调用一次通用注册：

public abstract class IntegrationTestBase<TService, TImplementation>
where TService : class
where TImplementation : class, TService
{
    protected TService Sut(Action<IServiceCollection>? configureService = default)
    {
        var services = new ServiceCollection();
        services.AddMockLogger(); // 替代原来的AddLogger<TImplementation>
        services.AddSut<TService, TImplementation>();

        configureService?.Invoke(services);

        return services.BuildServiceProvider().GetRequiredService<TService>();
    }
}

测试类里的InitServices也不用再手动加AddLogger<B>了：

private static void InitServices(IServiceCollection services, bool refreshTokenGrantEnabled = false, bool passwordGrantEnabled = false, bool stsEnabled = true)
{
     services.AddSingleton<B>();
     // 移除AddLogger<B>，通用Logger会自动处理
}

2. 基于Moq的通用注册方案 #

如果坚持用Mock.Of<ILogger<T>>，可以用包装类实现通用注册：

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddMockLogger(this IServiceCollection services)
    {
        services.AddSingleton(typeof(ILogger<>), typeof(MockLoggerWrapper<>));
        return services;
    }

    private class MockLoggerWrapper<T> : ILogger<T>
    {
        private readonly ILogger<T> _mockInstance;

        public MockLoggerWrapper()
        {
            _mockInstance = Mock.Of<ILogger<T>>();
        }

        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => _mockInstance.BeginScope(state);
        public bool IsEnabled(LogLevel logLevel) => _mockInstance.IsEnabled(logLevel);
        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
            => _mockInstance.Log(logLevel, eventId, state, exception, formatter);
    }
}

3. 额外优化：自动注册依赖链 #

如果想进一步减少InitServices的维护成本，可以用DI自动装配（比如Scrutor库扫描程序集注册服务），避免手动逐个添加依赖：

public abstract class IntegrationTestBase<TService, TImplementation>
where TService : class
where TImplementation : class, TService
{
    protected TService Sut(Action<IServiceCollection>? configureService = default)
    {
        var services = new ServiceCollection();
        services.AddMockLogger();
        services.AddSingleton<TService, TImplementation>();
        
        // 用Scrutor自动注册当前程序集内的所有服务（需先安装Scrutor包）
        services.Scan(scan => scan
            .FromAssemblyOf<TImplementation>()
            .AddClasses()
            .AsImplementedInterfaces()
            .WithSingletonLifetime());

        configureService?.Invoke(services);

        return services.BuildServiceProvider().GetRequiredService<TService>();
    }
}

这样类A依赖的类B会被自动注册，不用再手动写services.AddSingleton<B>()，减少配置变更的风险。

内容的提问来源于stack exchange，提问作者user1263981