合成后如何更改MEF中的一部分合成？

ISecurityService

IPrincipal GetPrincipal()

[Import]
public ISecurityService SecurityService {
    get; set;
}
[ImportMany]
public IEnumerable<ISectionPanel> ImportedPanels {
    get; set;
}
public ObservableCollection<ISectionPanel> Panels {
    get; set;
}
public void OnImportsSatisfied() {
    Panels.Clear();
    IPrincipal p = Thread.CurrentPrincipal;
    foreach (ISectionPanel sp in ImportedPanels.Where(sp => sp.RequiredRole == null || p.IsInRole(sp.RequiredRole))) {
        Panels.Add(p);
    }
}

Lazy<T>

Lazy<T>

RegisterInstance<T>(T t)

public static void Main(string[] args)
{
    using (var container = new CompositionContainer(...))
    {
        // phase 1: compose security service and initialize principal
        var securityService = container.GetExportedValue<ISecurityService>();
        securityService.InitializePrincipal();

        // phase 2: compose the rest of the application and start it
        var form = container.GetExportedvalue<MainForm>();
        Application.Run(form);
    }
}

RegisterInstance