WPF Merge ItemsSource Lists

Question

I am working with a 2 lists in a backend class. Each list is a different type. Would like to present the user with a single list (containing a union of both lists) of which when an item in this list is selected the item's details appear.

The code will look something like:

My backend class looks somethings like this

public ObservableCollection<Person> People {get;}
public ObservableCollection<Product> Products {get;}

My XAML Looks Something Like This

<ListBox x:Name="TheListBox" ItemsSource={Some Expression to merge People and Products}>
   <ListBox.Resources>
         People and Product Data Templates
   </ListBox.Resources>
</ListBox>
      ...
<ContentControl Content={Binding ElementName=TheListBox, Path=SelectedItem }>
   <ContentControl.Resources>
         Data Templates for showing People and Product details
   </ContentControl.Resources>
</ContentControl>

Any suggestions?

Answer 1

You can use a CompositeCollection for this. Have a look at this question.

Answer 2

I don't understand why you don't just have expose a property like this in your ViewModel:

ObservableCollection<object> Items 
{
  get 
  {
    var list = new ObservableCollection<object>(People);
    list.Add(Product);
    return list;
  }
}

and then in your xaml you do this:

<ListBox x:Name="TheListBox" ItemsSource={Binding Items}>
   <ListBox.Resources>
         People and Product Data Templates
   </ListBox.Resources>
</ListBox>
      ...
<ContentControl Content={Binding ElementName=TheListBox, Path=SelectedItem }>
   <ContentControl.Resources>
         Data Templates for showing People and Product details
   </ContentControl.Resources>
</ContentControl>

UPDATE:

If you need to manipulate your model differently do the following:

ObservableCollection<object> _Items 
ObservableCollection<object> Items 
{
  get 
  {
    if (_Items == null)
    {
      _Items = new ObservableCollection<object>();
      _Items.CollectionChanged += EventHandler(Changed);
    }
    return _Items;
  }
  set 
  { 
    _Items = value;
    _Items.CollectionChanged += new CollectionChangedEventHandler(Changed);
  }
}

void Changed(object sender,CollectionChangedEventArgs e)
{
  foreach(var item in e.NewValues)
  {
    if (item is Person)
      Persons.Add((Person)item);
    else if (item is Product)
      Products.Add((Product)item);
  }
}

This is just an example. But if you modify the above to meet your needs, it might get you to your goal