System.AddIn in WCF

Question

Hello,

I have a question about use AddIn framework, provided by .NET Framework (currently use 3.5 SP1) implemented in System.AddIn namespace. I build a prototype with simple AddIn. This AddIn is instantiated in business logic of WCF Service.

Implementation of business logic (only necessary code is shown):

internal class BusinessLayer : IBusinessLayer
{
    public object Execute(object toConvert, Operation operation)
    {
     IDictionary<string, AddInToken> tokens = AddIns.Store.GetAddInsTokens(@"c:\SomePathToStore");

     foreach (KeyValuePair<string, AddInToken> token in tokens)
     {
      if (operation.Name == token.Key && operation.Version == token.Value.Version)
      {
       ConversionHostView view = token.Value.Activate<ConversionHostView>(AddInSecurityLevel.FullTrust);

       object converted =  view.Convert(toConvert);

       AddInController.GetAddInController(view).Shutdown();

       return converted;
      }
     }

     throw new InvalidOperationException("No operation found!");
    }
    ...
}

Implementation of service (only necessary code is shown):

public class Service : IServiceContract
{
    IBusinessLayer bl;

    public Service()
    {
     bl = BL.BLFactory.GetBL();
    }

    public object Execute(object toConvert, ERES.ConversionService.Entity.Operation operation)
    {
     return bl.Execute(toConvert, operation);
    }
    ...
}

I created two Unit tests. One call direct method of business logic, other one WCF method. Direct call works fine, but if I activate AddIn from WCF i get this exception:

"Unable to cast transparent proxy to type 'ERES.ConversionService.Contract.IConversionContract'

Stack trace:

*at ConversionHostViewToContractAdapter_ConstructorInvoker(Object ) at System.AddIn.Hosting.AddInActivator.AdaptToHostT at System.AddIn.Hosting.AddInActivator.ActivateInAppDomainT at System.AddIn.Hosting.AddInActivator.ActivateT at System.AddIn.Hosting.AddInActivator.ActivateT at System.AddIn.Hosting.AddInActivator.ActivateT at System.AddIn.Hosting.AddInToken.ActivateT at ERES.ConversionService.BL.BusinessLayer.Execute(Object toConvert, Operation operation) in C:\Documents and Settings\kc\My Documents\Visual Studio 2008\Projects\ConversionServiceSolution\ERES.ConversionService.BL\BusinessLayer.cs:line 44 at ERES.ConversionService.Service.Execute(Object toConvert, Operation operation) in C:\Documents and Settings\kc\My Documents\Visual Studio 2008\Projects\ConversionServiceSolution\ERES.ConversionService\Service.svc.cs:line 25 at SyncInvokeExecute(Object , Object[] , Object[] ) at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs) at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)*

Any help?

Regards Anton Kalcik

UPDATE: I was able to go around this with this code:

ConversionHostView view = token.Value.Activate<ConversionHostView>(AppDomain.CurrentDomain);

So at this case is only possible to execute AddIn only at same AppDomain as service self. But I don't understand why?

Answer 1

Isn't that related to specified parameter for Activate method - AppDomain.CurrentDomain?