Question

So I have tried a whole bunch of examples from google, but I cannot seem to give my treeview checkboxes….The only thing I can think of is that it is because my tree’s ItemsSource is always changing

An example I was trying is: TreeView with Checkboxes

most noteable, the HierarchicalDataTemplate:

<HierarchicalDataTemplate 
  x:Key="CheckBoxItemTemplate"
  ItemsSource="{Binding Children, Mode=OneTime}"
  >
  <StackPanel Orientation="Horizontal">
    <!-- These elements are bound to a FooViewModel object. -->
    <CheckBox
      Focusable="False" 
      IsChecked="{Binding IsChecked}" 
      VerticalAlignment="Center"
      />
    <ContentPresenter 
      Content="{Binding Name, Mode=OneTime}" 
      Margin="2,0"
      />
  </StackPanel>
</HierarchicalDataTemplate> 

and I set my tree’s ItemTemplate to:

ItemTemplate="{StaticResource CheckBoxItemTemplate}"

But I see no checkboxes. I think it is because in the example, the data is bound to Children…but in my example, I am always changing the itemsSource (moving from tree to tree, or editting it, and adding it back to the tree etc)…

Anyone know how to make it work?

Thanks!

*EDIT*

adding the treeview itemsSource I just go

tv_master.ItemsSource = t.TreeItems;

Where the t.TreeItems is a List which holds the top level nodes..

my treeview:

<my:SpecTreeView Margin="8,8,0,12" 
                         x:Name="tv_local" 
                         TreeViewItem.Selected="node_Selected" HorizontalAlignment="Left" Width="304"
                         x:FieldModifier="private" BorderBrush="Black">

The original class used by the person who wrote the checkbox code:

using System.Collections.Generic;
using System.ComponentModel;

namespace TreeViewWithCheckBoxes
{
    public class FooViewModel : INotifyPropertyChanged
    {
        #region Data

        bool? _isChecked = false;
        FooViewModel _parent;

        #endregion // Data

        #region CreateFoos

        public static List<FooViewModel> CreateFoos()
        {
            FooViewModel root = new FooViewModel("Weapons")
            {
                IsInitiallySelected = true,
                Children =
                {
                    new FooViewModel("Blades")
                    {
                        Children =
                        {
                            new FooViewModel("Dagger"),
                            new FooViewModel("Machete"),
                            new FooViewModel("Sword"),
                        }
                    },
                    new FooViewModel("Vehicles")
                    {
                        Children =
                        {
                            new FooViewModel("Apache Helicopter"),
                            new FooViewModel("Submarine"),
                            new FooViewModel("Tank"),                            
                        }
                    },
                    new FooViewModel("Guns")
                    {
                        Children =
                        {
                            new FooViewModel("AK 47"),
                            new FooViewModel("Beretta"),
                            new FooViewModel("Uzi"),
                        }
                    },
                }
            };

            root.Initialize();
            return new List<FooViewModel> { root };
        }

        FooViewModel(string name)
        {
            this.Name = name;
            this.Children = new List<FooViewModel>();
        }

        void Initialize()
        {
            foreach (FooViewModel child in this.Children)
            {
                child._parent = this;
                child.Initialize();
            }
        }

        #endregion // CreateFoos

        #region Properties

        public List<FooViewModel> Children { get; private set; }

        public bool IsInitiallySelected { get; private set; }

        public string Name { get; private set; }

        #region IsChecked

        /// <summary>
        /// Gets/sets the state of the associated UI toggle (ex. CheckBox).
        /// The return value is calculated based on the check state of all
        /// child FooViewModels.  Setting this property to true or false
        /// will set all children to the same check state, and setting it 
        /// to any value will cause the parent to verify its check state.
        /// </summary>
        public bool? IsChecked
        {
            get { return _isChecked; }
            set { this.SetIsChecked(value, true, true); }
        }

        void SetIsChecked(bool? value, bool updateChildren, bool updateParent)
        {
            if (value == _isChecked)
                return;

            _isChecked = value;

            if (updateChildren && _isChecked.HasValue)
                this.Children.ForEach(c => c.SetIsChecked(_isChecked, true, false));

            if (updateParent && _parent != null)
                _parent.VerifyCheckState();

            this.OnPropertyChanged("IsChecked");
        }

        void VerifyCheckState()
        {
            bool? state = null;
            for (int i = 0; i < this.Children.Count; ++i)
            {
                bool? current = this.Children[i].IsChecked;
                if (i == 0)
                {
                    state = current;
                }
                else if (state != current)
                {
                    state = null;
                    break;
                }
            }
            this.SetIsChecked(state, false, true);
        }

        #endregion // IsChecked

        #endregion // Properties

        #region INotifyPropertyChanged Members

        void OnPropertyChanged(string prop)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
    }
}

My TNode Class

public class TNode : TreeViewItem{

    public int Level { get; set; }
    public Boolean IsCheckedStr { get; set; }
    public string Section { get; set; }
    public string Note { get; set; }
    public Boolean Locked { get; set; }
    public string ID { get; set; }
    public int Hierarchy { get; set; }
    public string Type { get; set; }
    public Boolean HasChildren { get; set; }
    public string TextBlock { get; set; }
    public Boolean ShowDetails { get; set; }
    public List<TNode> Dependencies { get; set; }
    public TNode(string id) {
        ID = id;
        Dependencies = new List<TNode>();
    }

I just want to get the checkboxes to appear for now 🙁

Let me know if there is anything else you would like to see

Answer 1

Edit: DataTemplates are for data, TreeViewItems or subclasses thereof are not data, the template will be ignored. You should see an error regarding this in the Output-window of Visual Studio (which is helpful for debugging databinding issues of any sort).

---

See nothing wrong with this, you might want to post the code behind for the classes, and the TreeView instance declaration.

A common error is the lack of notifying interfaces. Also: Did you bind the ItemsSource of the TreeView itself to a root-list of items?