NullToVisibilityConverter make visible if not null

public class NullVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value == null ? Visibility.Hidden : Visibility.Visible;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Then reference the NullVisibilityConverter in your XAML Resources.

<StackPanel.Resources>
  <simpleXamlContent:NullVisibilityConverter x:Key="NullToVisibilityConverter"/>
</StackPanel.Resources>

To use the converter we can create one in the resources, and refer to it as a static resource in the binding statement.

<UserControl xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit">
    <UserControl.Resources>
      <yournamespace:NullVisibilityConverter x:Key="NullToVisibilityConverter"/>
    </UserControl.Resources>

    <ListView>
    <!--here is list view-->
    </ListView>

    <xctk:PropertyGrid SelectedObject="{Binding Active}" Visibility="{Binding Active, Converter={StaticResource NullToVisibilityConverter}}" >  
    </xctk:PropertyGrid>
</UserControl>

and Converter class itself

public class NullVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value == null ? Visibility.Hidden : Visibility.Visible;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}