在 Autofac 中解析 HttpRequest 之外的 HttpRequestScoped 实例

发布于 2024-09-04 19:56:33 字数 1026 浏览 1 评论 0原文

假设我有一个注册为 HttpRequestScoped 的依赖项，因此每个请求只有一个实例。如何解决 HttpRequest 之外的相同类型的依赖关系？

例如：

// Global.asax.cs Registration
builder.Register(c => new MyDataContext(connString)).As<IDatabase>().HttpRequestScoped();
_containerProvider = new ContainerProvider(builder.Build());

// This event handler gets fired outside of a request
// when a cached item is removed from the cache.
public void CacheItemRemoved(string k, object v, CacheItemRemovedReason r)
{
    // I'm trying to resolve like so, but this doesn't work...
    var dataContext = _containerProvider.ApplicationContainer.Resolve<IDatabase>();
    // Do stuff with data context.
}

上面的代码在执行 CacheItemRemoved 处理程序时抛出 DependencyResolutionException：

没有范围与表达式“值(Autofac.Builder.RegistrationBuilder`3+<>c__DisplayClass0[MyApp.Core.Data.MyDataContext,Autofac.Builder.SimpleActivatorData,Autofac.Builder.SingleRegistrationStyle]).lifetimeScopeTag.Equals匹配(scope.Tag)' 在请求实例的范围内可见。

原文

Suppose I have a dependency that is registered as HttpRequestScoped so there is only one instance per request. How could I resolve a dependency of the same type outside of an HttpRequest?

For example:

// Global.asax.cs Registration
builder.Register(c => new MyDataContext(connString)).As<IDatabase>().HttpRequestScoped();
_containerProvider = new ContainerProvider(builder.Build());

// This event handler gets fired outside of a request
// when a cached item is removed from the cache.
public void CacheItemRemoved(string k, object v, CacheItemRemovedReason r)
{
    // I'm trying to resolve like so, but this doesn't work...
    var dataContext = _containerProvider.ApplicationContainer.Resolve<IDatabase>();
    // Do stuff with data context.
}

The above code throws a DependencyResolutionException when it executes the CacheItemRemoved handler:

No scope matching the expression 'value(Autofac.Builder.RegistrationBuilder`3+<>c__DisplayClass0[MyApp.Core.Data.MyDataContext,Autofac.Builder.SimpleActivatorData,Autofac.Builder.SingleRegistrationStyle]).lifetimeScopeTag.Equals(scope.Tag)' is visible from the scope in which the instance was requested.

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破晓 2024-09-11 19:56:33

InstancePerLifetimeScope()，而不是 HttpRequestScoped()，将给出您需要的结果。

但有一个警告 - 如果 IDatabase 需要处置，或者依赖于需要处置的东西，如果您从 ApplicationContainer 解析它，则不会发生这种情况。最好这样做：

using (var cacheRemovalScope =
        _containerProvider.ApplicationContainer.BeginLifetimeScope())
{
    var dataContext = cacheRemovalScope.Resolve<IDatabase>();
    // Do what y' gotta do...
}

InstancePerLifetimeScope(), rather than HttpRequestScoped(), will give the result you need.

There is a caveat though - if IDatabase requires disposal, or depends on something that requires disposal, this won't happen if you resolve it from the ApplicationContainer. Better to do:

using (var cacheRemovalScope =
        _containerProvider.ApplicationContainer.BeginLifetimeScope())
{
    var dataContext = cacheRemovalScope.Resolve<IDatabase>();
    // Do what y' gotta do...
}

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