using System;

using System.ComponentModel.Composition;

using System.ComponentModel.Composition.Hosting;

public class Program

{

    public static void Main()

    {

        using var catalog = new AssemblyCatalog(typeof(Program).Assembly);

        using var container = new CompositionContainer(catalog);

        var dummyInstance = container.GetExport<Foo>().Value;

        Console.WriteLine($"HasInstance: {dummyInstance is not null}");

        var export = container.GetExport<Foo>();

        Console.WriteLine($"IsValueCreated: {export.IsValueCreated}");

    }

}

​

[Export]

[PartCreationPolicy(CreationPolicy.Shared)]

public class Foo 

{

}