c# - 每个匹配生命周期范围的实例，默认？

Question

我想在 Autofac 中为每个匹配的生命周期范围的注册创建一个实例，但偶尔需要从全局容器请求一个实例（其中没有匹配的生命周期范围）。在不存在匹配生命周期范围的情况下，我想提供一个顶级实例而不是抛出异常。

这可能吗？

Answer 1

我认为您最好通过引入新的生命周期选项来扩展 Autofac。我拿了 Autofac 的源代码并做了一些修改：

public static class RegistrationBuilderExtensions
{
    public static IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> InstancePerMatchingOrRootLifetimeScope<TLimit, TActivatorData, TRegistrationStyle>(this IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> builder, params object[] lifetimeScopeTag)
    {
        if (lifetimeScopeTag == null) throw new ArgumentNullException("lifetimeScopeTag");
        builder.RegistrationData.Sharing = InstanceSharing.Shared;
        builder.RegistrationData.Lifetime = new MatchingScopeOrRootLifetime(lifetimeScopeTag);
        return builder;
    }
}

public class MatchingScopeOrRootLifetime: IComponentLifetime
{
    readonly object[] _tagsToMatch;

    public MatchingScopeOrRootLifetime(params object[] lifetimeScopeTagsToMatch)
    {
        if (lifetimeScopeTagsToMatch == null) throw new ArgumentNullException("lifetimeScopeTagsToMatch");

        _tagsToMatch = lifetimeScopeTagsToMatch;
    }

    public ISharingLifetimeScope FindScope(ISharingLifetimeScope mostNestedVisibleScope)
    {
        if (mostNestedVisibleScope == null) throw new ArgumentNullException("mostNestedVisibleScope");

        var next = mostNestedVisibleScope;
        while (next != null)
        {
            if (_tagsToMatch.Contains(next.Tag))
                return next;

            next = next.ParentLifetimeScope;
        }

        return mostNestedVisibleScope.RootLifetimeScope;
    }
}

只需将这些类添加到您的项目中并将您的组件注册为：

builder.RegisterType<A>.InstancePerMatchingOrRootLifetimeScope("TAG");

我自己没有尝试过，但它应该可以工作。

Answer 2

可能的解决方案是覆盖子生命周期范围内的注册。

样本：

public enum Scopes
{
    TestScope
}

public class Test
{
   public string Description { get; set; }
}

public class Tester
{
    public void DoTest()
    {
        ContainerBuilder builder = new ContainerBuilder();
        builder.RegisterType<Test>()
            .OnActivating(args => args.Instance.Description = "FromRoot")
            .SingleInstance();
        var container = builder.Build();

        var scope = container.BeginLifetimeScope(Scopes.TestScope, b => b
            .RegisterType<Test>()
            .InstancePerMatchingLifetimeScope(Scopes.TestScope)
            .OnActivating(args => args.Instance.Description = "FromScope"));

        var test1 = container.Resolve<Test>();
        Console.WriteLine(test1.Description); //writes FromRoot

        var test2 = scope.Resolve<Test>();
        Console.WriteLine(test2.Description); //writes FromScope

        Console.ReadLine();
    }
}

Answer 3

根容器本身是一个生命周期范围，其标签名称为: root，定义在LifetimeScope.RootTag

所以你可以这样做：

using Autofac.Core.Lifetime;

builder.RegisterType<Service>().As<IService>()
    .InstancePerMatchingLifetimeScope(LifetimeScope.RootTag, "foobar");