New Post: ServiceLocator.Current is null when using VSTO and MEF

Hi,My code like this

        MainWindowNavViewModel mainWindowNavViewModel1 = ServiceLocator.Current.GetInstance<MainWindowNavViewModel>();

           [Export(typeof(MainWindowNavViewModel))]
           public class MainWindowNavViewModel 
           {}

ServiceLocator.Current.GetInstance work well.

if code like this ,it dose now work.

        MainWindowNavViewModel mainWindowNavViewModel1 = ServiceLocator.Current.GetInstance<MainWindowNavViewModel>();

[Export(typeof(MainWindowNavViewModel))]
public class MainWindowNavViewModel : BaseNavViewModel
{   
}


public abstract class BaseNavViewModel
{
    [Import]
    public BaseMainViewModel MainViewModel { get; set; }
    public ObservableCollection<BaseNavViewModel> NavViewModelCollection { get; set; }
    public BaseNavViewModel()
    {
        NavViewModelCollection = new ObservableCollection<BaseNavViewModel>();
    }
}

BaseNavViewModel、MainWindowNavViewModel in diffrent namespace

Do you kown the reason,thanks