MEF - Show how a specific object instance can be injected into a container.

MEFExistingInstanceInjectionSample.cs

namespace MEFExistingInstanceInjection
{
    using System;
    using System.ComponentModel.Composition;
    using System.ComponentModel.Composition.Hosting;

    /// <seealso href="http://stackoverflow.com/questions/7684766/is-it-possible-to-inject-an-existing-instance-into-a-mef-plugin"/>
    class MEFExistingInstanceInjectionSample
    {
        static void Main(string[] args)
        {
            var container = new CompositionContainer(new TypeCatalog(typeof(Foo)));

            // Inject THE one and only instance
            var instance = new Foo("Hello world");
            container.ComposeExportedValue<IFoo>(instance);

            var foo = container.GetExportedValue<IFoo>();
            Console.WriteLine(foo.Value);
        }
    }

    public interface IFoo { string Value { get; } }

    [Export(typeof(IFoo))]
    public class Foo : IFoo 
    {
        public Foo(string value) { this.Value = value; }

        public string Value { get; private set; }
    }
}