Resolving HttpRequestScoped Instances outside of a HttpRequest in Autofac
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 wh开发者_如何学Cen 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.
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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