MEF Composition Import Issue

0
votes

I have a MEF composition question. In my development environment I am able to use this code to import parts.

var dirCatalog = new DirectoryCatalog(path, "MyCompany.*.dll");            
var container = new CompositionContainer(dirCatalog);
container.SatisfyImportsOnce(this);

However when I deploy to a test server that doesn't work. The only way I have found to make it work right is to explicitly load the the dlls that have exports like this:

var catalog = new AggregateCatalog();
catalog.Catalogs.Add(new AssemblyCatalog(Assembly.LoadFrom(Path.Combine(path, "MyCompany.Services.AppServer.Modelling.dll"))));
catalog.Catalogs.Add(new AssemblyCatalog(Assembly.LoadFrom(Path.Combine(path, "MyCompany.IFS.AppServer.Dispatchers.dll"))));
catalog.Catalogs.Add(new AssemblyCatalog(Assembly.LoadFrom(Path.Combine(path, "MyCompany.Services.AppServer.Service.dll"))));
catalog.Catalogs.Add(new AssemblyCatalog(Assembly.LoadFrom(Path.Combine(path, "MyCompany.IFS.Common.InstrumentService.Proxy.dll"))));
catalog.Catalogs.Add(new AssemblyCatalog(Assembly.LoadFrom(Path.Combine(path, "MyCompany.IFS.Common.InstrumentPropertyService.Proxy.dll"))));

var container = new CompositionContainer(catalog);
container.SatisfyImportsOnce(this);

Obviously, I don't really want to explicitly load every dll that has an export in it; that sort of defeats the purpose of MEF. But, right now that's the only thing I have found that works.

This code is in a custom service host factory used for starting a WCF service hosted in IIS. Not sure that that matters...

TIA, Greg

1
mef

1 Answers

0
votes

Why not put the DLL file names inside an XML or other config file. At least you won't have to recompile.

I'd suggest having at least..

Filename and IsEnabled, that way you can just toggle IsEnabled instead of having to comment in the XML file.