How i can solve COMException at the relaycommand? Do I miss something?

Question

I have a UWP WinRt App.

I use MVVM Light.

I have a ListView on the MainPage. When I press on a Item with A x:Bind RelayCommand i go to a DetailsView of the Item. If I debug on a Lumia 635 I got an Error after pressing on a Item three times.

=> I press on a Item => go to DetailsView and then i press Back and repeat this, but third time pressing it the error occurs.

I never execute the command. After three Times I got this Error. Its in the constructor of the DetailsViewModel.

If I comment this out, another RelayCommand raise this exception.. so I think i forgot something to implement and I dont get it..

Detail:

My Service in the Portable Project looks like this

 public interface ISystemcontactsService
{
    bool CanAdd { get; }
    Task AddContactToSystemcontacts(Contact contact);
}

My implementation in the UWP Project:

public class UwpSystemcontactsService : ISystemcontactsService
{
public bool CanAdd => false;

    public async Task AddContactToSystemcontacts(BL.Model.Contact contact)
    {

    }
}

My ViewModelLocator

public class UwpViewModelLocator : ViewModelLocator
{

    static UwpViewModelLocator()
    {
        //if (!GalaSoft.MvvmLight.ViewModelBase.IsInDesignModeStatic)
        {
            SimpleIoc.Default.Register<INavigationService>(CreateUwpNavigationService);
            SimpleIoc.Default.Register<ICallerService, UwpCallerService>();
            SimpleIoc.Default.Register<IEmailerService, UwpEmailerService>();
            SimpleIoc.Default.Register<IConnectivityCheckerService, ConnectivityCheckerService>();
            SimpleIoc.Default.Register<ILocationService, UwpLocationService>();
            SimpleIoc.Default.Register<ISystemcontactsService, UwpSystemcontactsService>();
            SimpleIoc.Default.Register<IAddressResolverService, UwpAddressResolverService>();

        }
    }
    static INavigationService CreateUwpNavigationService()
    {
        var navigationService = new UwpNavigationService();

        navigationService.Configure(Navigation.Details, typeof(DetailPage));
        navigationService.Configure(Navigation.Main, typeof(MainPage));

        return navigationService;
    }
}

The implementation in the DetailsViewModel

public class DetailsViewModel : ViewModelBase
{
    private readonly ISystemcontactsService _contactService;

   public DetailsViewModel(ISystemcontactsService contactService)
{

   PropertyChanged += (sender, args) =>
        {
                if (args.PropertyName == nameof(CanAddContactToSystemContacts)) ((RelayCommand)AddContactToSystemContactsCommand).RaiseCanExecuteChanged();
        };

        AddContactToSystemContactsCommand = new RelayCommand(AddContactToSystemContacts, () => CanAddContactToSystemContacts);

   }

    public bool CanAddContactToSystemContacts => _contactService.CanAdd && Contact != null;

    public ICommand AddContactToSystemContactsCommand { get; private set; }


    private void AddContactToSystemContacts()
    {
        _contactService.AddContactToSystemcontacts(Contact);
    }

XAML - DetailPage

<AppBarButton Icon="SaveLocal"
                          Label="Lokal Speichern"
                          Command="{x:Bind   ViewModel.AddContactToSystemContactsCommand}" />

WinRT, C#, UWP, MVVM-Light, Fody, Win10

How i can solve COMException at the relaycommand? Do I miss something?

0 Answers0