Public Class Test2
    <Import()>
    Public Property data As Test1
End Class

Sub Main()
    Dim catalog As New DirectoryCatalog(".")
    Dim container As New CompositionContainer(catalog)
    Dim test As New Test2()
    container.SatisfyImportsOnce(test)
    Console.WriteLine(test.data.data)
    Console.ReadLine()
End Sub

public class Test2
{
    [Import]
    public Test1 data { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        DirectoryCatalog catalog = new DirectoryCatalog(".");
        CompositionContainer container = new CompositionContainer(catalog);
        Test2 test = new Test2();
        container.SatisfyImportsOnce(test);
        Console.WriteLine(test.data.data);
        Console.ReadLine();
    }
}

<Export()>
Public Class Test1
    Public ReadOnly Property data As String
        Get
            Return "The data!"
        End Get
    End Property
End Class

[Export]
public class Test1
{
    public String data = "The data!";
}