View

<Window x:Class="Vivenda.Views.TransferUtilitiesWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Kies een pand" Height="300" Width="550"
        DataContext="{Binding TransferUtilitiesWindowViewModel, RelativeSource={RelativeSource Self}}">
    <Grid>
        <GroupBox Header="Info" Margin="10,71,10,0" VerticalAlignment="Top" Height="163" Visibility="{Binding Path=DocumentType, Converter={StaticResource ConnectionToVisibilityConverter}, FallbackValue=Visible}" >
            <Grid />
        </GroupBox>
        <ComboBox HorizontalAlignment="Left" Margin="115,10,0,0" VerticalAlignment="Top" Width="420" ItemsSource="{Binding Source={StaticResource documentTypes},Path=DisplayNames}"
                                              SelectedItem="{Binding Path=DocumentType, Converter={StaticResource documentTypes}}" />
        <Label Content="Document" HorizontalAlignment="Left" Margin="10,8,0,0" VerticalAlignment="Top" Width="100"/>
    </Grid>
</Window>

VM

namespace Vivenda.ViewModels
{
    public class TransferUtilitiesWindowViewModel //: INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        public List<Premise> Premises { get; private set; }
        public Premise Premise { get; set; }
        private bool? _isBusiness;

        public bool? IsBusiness
        {
            get { return _isBusiness; }
            set
            {
                _isBusiness = value;
                if(_isBusiness == true)
                {
                    BusinessData = new BusinessData();
                    NotifyPropertyChanged("IsBusiness");
                } else
                {
                    BusinessData = null;
                }
            }
        }

        public BusinessData BusinessData { get; set; }
        public UtilityDocumentType DocumentType { get; set; }

        public TransferUtilitiesWindowViewModel()
        {
            Premises = VivendaContext.Current.Premises.ToList();
        }
    }
}