IServiceProvider.GetServices<T>() 是否始终返回注册顺序中的可用服务实现？

Question

这个问题具体指的是ASP.NET core 3.1和内置的依赖注入容器（Microsoft DI）。

此Microsoft 文档和此 stackoverflow 问题IEnumerable<TService>确认，当为同一服务类型注册多个实现类型时，Microsoft DI 容器始终通过遵守注册顺序进行解析。订单是有保证的，并且有明确的记录。

有谁知道该方法是否同样适用IServiceProvider.GetServices<T>()？

如果上述问题的答案是肯定的，那么即使在以下示例中（同一类的两个不同实例注册为同一服务类型的实现），这也成立吗？

public interface IService {}

public sealed class Foo : IService {}

var foo1 = new Foo();
var foo2 = new Foo();

services.AddSingleton<IService>(foo1);
services.AddSingleton<IService>(foo2);

var implementations = serviceProvider.GetServices<IFoo>();

// is it guaranteed that implementations[0] == foo1 and implementations[1] == foo2 ???

Answer 1

简短的答案是肯定的，因为内部GetServices* 扩展方法的解析与具有注入依赖项的IEnumerable<T>构造函数中的解析相同IEnumerable<T>

/// <summary>
/// Get an enumeration of services of type <typeparamref name="T"/> from the <see cref="IServiceProvider"/>.
/// </summary>
/// <typeparam name="T">The type of service object to get.</typeparam>
/// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the services from.</param>
/// <returns>An enumeration of services of type <typeparamref name="T"/>.</returns>
public static IEnumerable<T> GetServices<T>(this IServiceProvider provider)
{
    if (provider == null)
    {
        throw new ArgumentNullException(nameof(provider));
    }

    return provider.GetRequiredService<IEnumerable<T>>();
}
/// <summary>
/// Get an enumeration of services of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/>.
/// </summary>
/// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the services from.</param>
/// <param name="serviceType">An object that specifies the type of service object to get.</param>
/// <returns>An enumeration of services of type <paramref name="serviceType"/>.</returns>
public static IEnumerable<object?> GetServices(this IServiceProvider provider, Type serviceType)
{
    if (provider == null)
    {
        throw new ArgumentNullException(nameof(provider));
    }

    if (serviceType == null)
    {
        throw new ArgumentNullException(nameof(serviceType));
    }

    Type? genericEnumerable = typeof(IEnumerable<>).MakeGenericType(serviceType);
    return (IEnumerable<object>)provider.GetRequiredService(genericEnumerable);
}

源代码