Question

Just wanted to know if what I’m trying to do is possible since I couldn’t find any information about it in the net.

Lets say I got a class that I export with PartCreationPolicy(CreationPolicy.Any).
If I’d like to import it with ServiceLocator.Instance.GetInstance(), where can I specify with which CreationPolicy I’d like to import it? (If it would be Shared or NonShared)

Just couldn’t find any info about it anywhere.

Thanks!

Answer 1

As I understand it this can’t be specified through a generic service locator.

By default, CreationPolicy.Any will be treated as ‘shared’. To get a ‘non-shared’ instance you need to either:

• Change the creation policy on the part to CreationPolicy.NonShared; or,
• Use the MEF CompositionContainer.GetExports(ImportDefinition) method; or,
• Create a part that uses an ExportFactory import and request that from the ServiceLocator (see below. Requires MEF 2, or Silverlight 4 – not available in the .NET 4.0 RTM MEF.)

The kind of thing you need for the third option would look like:

[Export]
public class ExportFactoryProvider<T>
{
    [Import]
    public ExportFactory<T> Factory { get; set; }
}

Then, request one of these from the service locator and use the factory property to create new instances (where IService is the thing you want to instantiate new instances of):

var serviceFactory =
    ServiceLocator.Instance.GetService<ExportFactoryProvider<IService>>();

using (var service1 = serviceFactory.Factory.CreateExport())
{
    DoSomething(service1.Value);
}

Admittedly this ends up looking a bit hacky. I believe the reason for the awkwardness is that few (no?) other IoC containers support specifying anything like CreationPolicy when a service is requested.