Unity容器声明周期管理

Having said that, here is a solution that you can use with the Unity container:

Create some custom attributes for the different lifetime styles that you want to have like this:

[AttributeUsage(AttributeTargets.Class)]
public class SingletonAttribute : Attribute
{

}

[AttributeUsage(AttributeTargets.Class)]
public class TransientAttribute : Attribute
{

}

You can have these attributes in some common library and reference it from your service class libraries.

Then, apply these attributes to your service classes in your class libraries like in your question:

[Singleton]
public class ServiceImplA : IService
{}

[Transient]
public class ServiceImplB : IService
{}

Now, define a helper method that can get the lifetime manager based on reflection like this:

public static LifetimeManager GetLifeTimeManager<T>()
{
    Type type = typeof (T);

    if(type.GetCustomAttribute(typeof(TransientAttribute)) != null)
        return new TransientLifetimeManager();

    if (type.GetCustomAttribute(typeof(SingletonAttribute)) != null)
        return new ContainerControlledLifetimeManager();

    //Add more cases here

    return new TransientLifetimeManager(); //Default is transient
}

And use it like this:

container.RegisterType<IService, ServiceImplA>(GetLifeTimeManager<ServiceImplA>());

By the way, this solution is DI container independent. I mean that the attributes themselves are not specific to any container. It is the GetLifeTimeManager helper method that is specific to the Unity container. But you can use other DI containers and define similar helper methods for them.

You can also create extension methods to hide the invocation of the helper method like this:

public static IUnityContainer RegisterTypeWithLifeTime<TFrom, TTo>(this IUnityContainer container) where TTo : TFrom
{
    return container.RegisterType<TFrom, TTo>(GetLifeTimeManager<TTo>());
}

And use it like this:

container.RegisterTypeWithLifeTime<IService, ServiceImplA>();

You just need to constrain the types returned to types that are annotated with the Singletonattribute:

container.RegisterTypes(
    AllClasses.FromLoadedAssemblies()
        .Where(t => t.GetCustomAttributes<SingletonAttribute>(true).Any()),
    WithMappings.FromMatchingInterface,
    WithName.Default,
    WithLifetime.ContainerControlled);

You could register everything and then overwrite the registration for any singletons with a ContainerControlledLifetimeManager:

// Register All Types by Convention by default
container.RegisterTypes(
    AllClasses.FromLoadedAssemblies(),
    WithMappings.FromMatchingInterface,
    WithName.Default,
    WithLifetime.Transient);

// Overwrite All Types marked as Singleton
container.RegisterTypes(
    AllClasses.FromLoadedAssemblies()
        .Where(t => t.GetCustomAttributes<SingletonAttribute>(true).Any()),
    WithMappings.FromMatchingInterface,
    WithName.Default,
    WithLifetime.ContainerControlled,
    null,
    true); // Overwrite existing mappings without throwing

Another Container：

using System;
using System.Reflection;
using SimpleInjector.Advanced;

// Attribute for use by the application
public enum CreationPolicy { Transient, Scoped, Singleton }

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface,
    Inherited = false, AllowMultiple = false)]
public sealed class CreationPolicyAttribute : Attribute {
    public CreationPolicyAttribute(CreationPolicy policy) {
        this.Policy = policy;
    }

    public CreationPolicy Policy { get; private set; }
}

// Custom lifestyle selection behavior
public class AttributeBasedLifestyleSelectionBehavior : ILifestyleSelectionBehavior {
    private const CreationPolicy DefaultPolicy = CreationPolicy.Transient;

    public Lifestyle SelectLifestyle(Type serviceType, Type implementationType) {
        var attribute = implementationType.GetCustomAttribute<CreationPolicyAttribute>()
            ?? serviceType.GetCustomAttribute<CreationPolicyAttribute>();

        switch (attribute != null ? attribute.Policy : DefaultPolicy) {
            case CreationPolicy.Singleton: return Lifestyle.Singleton;
            case CreationPolicy.Scoped: return Lifestyle.Scoped;
            default: return Lifestyle.Transient;
        }
    }
}

// Usage
var container = new Container();
container.Options.DefaultScopedLifestyle = new WebRequestLifestyle();

container.Options.LifestyleSelectionBehavior =
    new AttributeBasedLifestyleSelectionBehavior();

container.Register<IUserContext, AspNetUserContext>();

// Usage in application
[CreationPolicy(CreationPolicy.Scoped)]
public class AspNetUserContext : IUserContext {
    // etc
}