After seeing Glenn Block talk about MEF in phoenix last week, I began to write a demo for work.

We have a pretty big pain point in our flagship product at work and I think that MEF would be a great way to alleviate that pain. Specifically, I would love to be able to just simply script that part of the application.

Enter Nicholas Blumhardt’s post about hosting IronRuby parts in MEF.

Nick has done quite a great job getting this to work. I had to update his code very little to use the latest version of MEF and the DLR.

Specifically, I had to add the “ExportTypeIdentity” metadata value to all ruby objects being exported.

  1: def self.export(cname, attrs={})
  2:
  3:   if cname.is_a?(Module)
  4:     include cname
  5:   end
  6:
  7:   attrs["ExportTypeIdentity"]=contract_name(cname)
  8:
  9:   export_attr(cname, attrs) do
 10:     self
 11:   end
 12: end
 13:
 14: def self.create_export_def(cname, attrs, accessor)
 15:   metadata = System::Collections::Generic::Dictionary[System::String,System::Object].new
 16:   attrs.each{|key, value| metadata.add key, value}
 17:   RubyExportDefinition.new(contract_name(cname), metadata, accessor)
 18: end

This works freaking great in my little test console app. But, it will not work for some reason in a web context. And as luck would have it, our flagship product is a web application.

This is the error I can’t seem to get around.

1) The export ‘ClassLibrary1.IContract’ is not assignable to type ‘ClassLibrary1.IContract’.

Has anyone made this work?

Download a demo here