C# WPF managing nested structures using ItemsControl

Question

So, I have already posted a question about the nested controls structure in WPF, it is here: Nested controls structure - in XAML or C#? And I have received a solution as follows:

<ItemsControl ItemsSource="{Binding SomeCollectionOfViewModel}">
   <ItemsControl.ItemsPanel>
      <ItemsPanelTemplate>
         <UniformGrid/>
      </ItemsPanelTemplate>
   </ItemsControl.ItemsPanel>
   <ItemsControl.ItemTemplate>
       <DataTemplate>
          <ItemsControl ItemsSource="{Binding SomeCollection}">   <!-- Nested Content -->
              ...
       </DataTemplate>
   <ItemsControl.ItemTemplate>
</ItemsControl>

I have used that solution, comming up with this:

<!-- The UniformGrids - boxes -->
<ItemsControl ItemsSource="{Binding UniformGridCollection}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <UniformGrid />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>

        <ItemsControl.ItemTemplate>
            <DataTemplate>

                <!-- The TextBoxes - Cells -->
                <ItemsControl ItemsSource="{Binding TextBoxCollection}">
                    <ItemsControl.ItemsPanel>
                        <ItemsPanelTemplate>
                            <UniformGrid />
                        </ItemsPanelTemplate>
                    </ItemsControl.ItemsPanel>
                </ItemsControl>

            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>

Here is the C# side:

public partial class MainWindow : Window
    {
        private readonly ObservableCollection<UniformGrid> uniformGridCollection = new ObservableCollection<UniformGrid>();
        public ObservableCollection<UniformGrid> UniformGridCollection { get { return uniformGridCollection; } }
        private readonly ObservableCollection<UniformGrid> textBoxCollection = new ObservableCollection<UniformGrid>();
        public ObservableCollection<UniformGrid> TextBoxCollection { get { return textBoxCollection; } }
        public MainWindow()
        {
            InitializeComponent();
            for (int i = 1; i <= 9; i++)
            {
                UniformGrid box = new UniformGrid();
                UniformGridCollection.Add(box);
                UniformGrid cell = new UniformGrid();
                TextBoxCollection.Add(cell);
            }
            DataContext = this;
        }
    }

But somehow the "Cells" - textboxes, that are inside the uniformgrids, do not create. Instead, I get only 9 uniform grids contain in one big uniform Grid (specified in Paneltemplate). I have checked the prgram with Snoop v 2.8.0: http://i40.tinypic.com/htzo5l.jpg

The question is: Could somebody tell me, why the inside structure(textboxes) arent created?

Answer 1

You're not defining any TextBox es anywhere, That's why you're not getting any TextBox es in the Visual Tree:

<Window x:Class="MiscSamples.NestedItemsControls"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="NestedItemsControls" Height="300" Width="300">
    <ItemsControl ItemsSource="{Binding Level1}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <UniformGrid/>
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <ItemsControl ItemsSource="{Binding Level2}">
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <TextBox Text="{Binding Value}"/> <!-- You Are missing this! -->
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Window>

Also, as mentioned in the comment, your Collections should be of ViewModel or Model types, not UI types:

ViewModels:

public class NestedItemsViewModel
{
    public List<Level1Item> Level1 { get; set; }
}

public class Level1Item
{
    public List<Level2Item> Level2 { get; set; }
}

public class Level2Item
{
    public string Value { get; set; }
}

Code Behind:

public partial class NestedItemsControls : Window
{
    public NestedItemsControls()
    {
        InitializeComponent();

        DataContext = new NestedItemsViewModel()
                          {
                              Level1 = Enumerable.Range(0, 10)
                                                 .Select(l1 => new Level1Item()
                                                    {
                                                        Level2 = Enumerable.Range(0, 10)
                                                                           .Select(l2 => new Level2Item { Value = l1.ToString() + "-" + l2.ToString() })
                                                                           .ToList()
                                                    })
                                                  .ToList()
                          };
    }
}

Notice that you will have to change the List s to ObservableCollection s if you expect these collections to change dynamically during runtime.

Also notice you have to implement INotifyPropertyChanged properly.