private void ContactAddClick(object sender, RoutedEventArgs e)
        {
            ContactsVM contacts = new ContactsVM {
                IsPartnerAdd = ((PartnerFormVM)DataContext).ChosenPartner.ID, PartnerContactList = ((PartnerFormVM)DataContext).ContactsList
            };
            PartnersWindow partners = new PartnersWindow {
                DataContext = contacts, Title = "Elérhetőségek"
            };

            contacts.LoadPartnersList();
            partners.ShowDialog();
        }