MEF - Export Module not loaded

Question

Following MEF Export will not be loaded by ComposeParts(this).

using MyLib;
using System.Composition;

namespace Test
{
    [Export(typeof(IExtension))]
    public class Test : IExtension
    {
    }
}

Answer 1

This happens when you auto-install MEF to dotnetcore using Visual Studio Alt+Enter menu. The correct namespace is System.ComponentModel.Composition. Due to quite similarly named namespace this may be overseen.

using MyLib;
using System.ComponentModel.Composition; // <--

namespace Test
{
    [Export(typeof(IExtension))]
    public class Test : IExtension
    {
    }
}