TreeView with CheckBoxes WPF - wpf

Question

I tried this sample How to develop treeview with checkboxes in wpf? to create a TreeView with checkbox but in this example you cannot have a family in another family.
So my question is how to create a full treeview with check box not only limited in one level?
So this is what I did
IParent.cs
interface IParent<T>
{
IEnumerable<T> GetChildren();
}
DataModel.cs
using System;
using System.Collections.Generic;
using System.Windows;
public class Family : DependencyObject, IParent<object>
{
public string Name { get; set; }
public List<Person> Members { get; set; }
IEnumerable<object> IParent<object>.GetChildren()
{
return Members;
}
}
public class Person : DependencyObject
{
public string Name { get; set; }
}
ItemHelper.cs
using System.Linq;
using System.Windows;
public class ItemHelper : DependencyObject
{
public static readonly DependencyProperty IsCheckedProperty =
DependencyProperty.RegisterAttached("IsChecked", typeof(bool?), typeof(ItemHelper),
new PropertyMetadata(false, new PropertyChangedCallback(OnIsCheckedPropertyChanged)));
private static void OnIsCheckedPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
IParent<object> sect = d as IParent<object>;
DependencyObject depObj = d as DependencyObject;
if (sect != null)
{
if (((bool?)e.NewValue).HasValue)
{
foreach (DependencyObject p in sect.GetChildren())
{
SetIsChecked(p, (bool?)e.NewValue);
}
}
}
if (depObj != null)
{
var parentObject = depObj.GetValue(ParentProperty) as IParent<object>;
var parentDO = depObj.GetValue(ParentProperty) as DependencyObject;
int ch = parentObject?.GetChildren()?.Where(
x => GetIsChecked(x as DependencyObject) == true).Count() ?? 0;
int un = parentObject?.GetChildren()?.Where(
x => GetIsChecked(x as DependencyObject) == false).Count() ?? 0;
if (un > 0 && ch > 0)
{
SetIsChecked(parentDO, null);
return;
}
if (ch > 0)
{
SetIsChecked(parentDO, true);
return;
}
SetIsChecked(parentDO, false);
}
}
public static void SetIsChecked(DependencyObject element, bool? IsChecked)
{
element?.SetValue(IsCheckedProperty, IsChecked);
}
public static bool? GetIsChecked(DependencyObject element)
{
return (bool?)element?.GetValue(IsCheckedProperty);
}
public static readonly DependencyProperty ParentProperty =
DependencyProperty.RegisterAttached("Parent", typeof(object), typeof(ItemHelper));
public static void SetParent(DependencyObject element, object Parent)
{
element?.SetValue(ParentProperty, Parent);
}
public static object GetParent(DependencyObject element)
{
return element?.GetValue(ParentProperty);
}
}
MainWindow.xaml
<Window x:Class="WpfApplication102.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication102"
Title="MainWindow" Height="220" Width="250">
<StackPanel>
<TreeView x:Name="treeView" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=Families}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local:Family}" ItemsSource="{Binding Members}" >
<CheckBox Content="{Binding Name}" IsChecked="{Binding Path=(local:ItemHelper.IsChecked), Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<CheckBox.Style>
<Style TargetType="{x:Type CheckBox}">
<Setter Property="Foreground" Value="Black"/>
<Setter Property="Visibility" Value="Visible"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=(local:ItemHelper.IsChecked)}" Value="False" >
<Setter Property="Foreground" Value="LightGray"/>
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type local:Person}" >
<CheckBox Content="{Binding Name}" IsChecked="{Binding Path=(local:ItemHelper.IsChecked), Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<CheckBox.Style>
<Style TargetType="{x:Type CheckBox}">
<Setter Property="Foreground" Value="Black"/>
<Setter Property="Visibility" Value="Visible"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=(local:ItemHelper.IsChecked)}" Value="False" >
<Setter Property="Foreground" Value="LightGray"/>
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
</DataTemplate>
</TreeView.Resources>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="True"/>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
<Button Content="?" Click="Button_PrintCrew_Click" />
<TextBlock x:Name="textBoxCrew"/>
</StackPanel>
</Window>
MainWindow.xaml.cs
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication102
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public ObservableCollection<Family> Families { get; set; }
public MainWindow()
{
InitializeComponent();
this.Families = new ObservableCollection<Family>();
this.Families.Add(new Family() { Name = "Simpsons", Members = new List<Person>() { new Person() { Name = "Homer" }, new Person() { Name = "Bart" } } });
this.Families.Add(new Family() { Name = "Griffin", Members = new List<Person>() { new Person() { Name = "Peter" }, new Person() { Name = "Stewie" } } });
this.Families.Add(new Family() { Name = "Fry", Members = new List<Person>() { new Person() { Name = "Philip J." } } });
foreach (Family family in this.Families)
foreach (Person person in family.Members)
person.SetValue(ItemHelper.ParentProperty, family);
}
private void Button_PrintCrew_Click(object sender, RoutedEventArgs e)
{
string crew = "";
foreach (Family family in this.Families)
foreach (Person person in family.Members)
if (ItemHelper.GetIsChecked(person) == true)
crew += person.Name + ", ";
crew = crew.TrimEnd(new char[] { ',', ' ' });
this.textBoxCrew.Text = "Your crew: " + crew;
}
}
}

Answer 1

Like many other aspects of WPF development, this becomes much easier if you follow the MVVM pattern.
Create a common ViewModel base class to represent each node of the tree, with a collection of the same type to represent the node's children. This is where you would include the logic to handle ticking / unticking the parent / child items as appropriate. The TreeView's ItemSource is then bound to a simple collection of items to form the root level. The U.I. layout of the View is defined by a HierachicalDataTemplate for each distinct node type.
I covered this in a recent blog post, with sample code here.