CODEWITHSUNDEEP
c#mef
DavidB
DavidB

Reputation: 2596

MEF not providing object

Update:

This is an mvc plugin project, using MEF to get the controllers and actions at run time. http://www.fidelitydesign.net/?p=104

I added a new project and in its class I added an export of a type that is already being composed. 

  [Export(typeof(IController)), ExportMetadata("Name", "Clocks")]
  public class ClocksController : Controller
  {

    public XmlActionResult Index()
    {
     var p = DeviceLogic.GetUnassigned;
    }
  [Import(typeof(DeviceLogic))]
  DeviceLogic DeviceLogic { get; set; }
  }

This gets composed in another project:

  [Export]
  public class ImportControllerFactory : DefaultControllerFactory
  {
    [ImportMany]
    private IEnumerable<PartFactory<IController, IControllerMetadata>> ControllerFactories;
  }

Application Start

[ImportMany]
private IEnumerable<ImportControllerFactory> ControllerFactories;

Controller factories is null, until I actually compose the parts

container.ComposeParts(this);

thats working fine, so I decided to try and emulate this to get devicelogic to appear in the project im having trouble with.

I created an emptry interface (IEmpty) for testing and tried this:

  [Export(typeof(IEmpty))]
  public class RequestProcessor : IEmpty
  {

    [Import(typeof(DeviceLogic))]
    DeviceLogic DeviceLogic { get; set; }
  }

and in my applciation start added

[ImportMany]
private IEnumerable<IEmpty> TestMef;

This is filled with the one instance after composition, so this seems to have worked. My question is does anyone have any suggestions as to why devicelogic is null in requestprocessor but not in clocksController.

Upvotes: 0

Views: 134

Answers (1)

Luke Marlin
Luke Marlin

Reputation: 1398

You need to call MEF's SatisfyImportsOnce method after your instantiation :

YourMEFContainter.SatisfyImportsOnce(dataTransfer)

Upvotes: 1

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