Develop Reference

WPF: TreeView does not show any children

I've been trying to get my first TreeView to work, at first without the ViewModel. But no matter what I do, it doesn't show any children, even though the binding is correct.
I'm using two Item templates, one for hierarchical and another for data. You can see the important parts for both below:
class GrupoTag
{
public string Nome { get; set; }
public GrupoTag Pai { get; set; }
public List<Tag> ListaFilhos { get; set; }
public List<GrupoTag> SubGrupos { get; set; }
public GrupoTag(string nome)
{
Nome = nome;
ListaFilhos = new List<Tag>();
SubGrupos = new List<GrupoTag>();
}
public List<object> Filhos
{
get
{
List<object> lista = new List<object>();
foreach (GrupoTag subGrupo in SubGrupos)
lista.Add(subGrupo);
foreach (Tag filho in ListaFilhos)
lista.Add(filho);
}
}
}
class Tag
{
public GrupoTag Pai { get; set; }
public string Nome { get; set; }
public Tag(string nome)
{
Nome = nome;
}
public Tag(GrupoTag pai, string nome)
{
Pai = pai;
Nome = nome;
}
}
The XAML binding to all of this:
<TreeView Name="MenuTags">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="xml2Excel2:GrupoTag" ItemsSource="{Binding Filhos}">
<TextBlock Text="{Binding Nome}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="xml2Excel2:Tag">
<TextBlock Text="{Binding Nome}" />
</DataTemplate>
</TreeView.Resources>
</TreeView>
But the property "Filhos" on the GrupoTag class is never accessed. I've tried putting a breakpoint in there, throwing an exception, but it's simply never called. And the TreeView only displays the names of the collection of GrupoTags I assigned to it as its ItemSource in code-behind.
MenuTags.ItemsSource = arvoreTeste.SubGrupos;
I've read all the related questions and corrected the code for the respective errors, but I'm still lost here.
EDIT 1: So I modified the code of the classes to conform to the simple interface below:
class ITag
{
public string Nome { get; set; }
public ObservableCollection<ITag> Filhos { get; set; }
}
As per Benin comment, GrupoTag now uses a single property stored in a ObservableCollection to represent its children. And, as per Adnan answer removed the DataType from the XAML TreeView. Now it looks like this:
<TreeView Name="ArvoreTags">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<TextBlock Text="{Binding Nome}" />
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
It works, the TreeViewis functional. But I don't know why.

You need to give your TreeView ItemSource and DataType. And I would agree to Berins comment , you should avoid making new list to each access to Filhos property. TreeView works very good with Polymorphis, I mean with data types.
<TreeView DockPanel.Dock="Top"
DataContext="{Binding ProjectNodes_DataContext}"
ItemsSource="{Binding Nodes}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local:ProjectNode}" ItemsSource="{Binding SubItems}">
<StackPanel>
<TextBlock Text="{Binding Header}"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.Resources>
My Property is:
private ProjectNodesVM mProjectNodes_DataContext;
public ProjectNodesVM ProjectNodes_DataContext
{
get { return mProjectNodes_DataContext; }
protected set
{
SetProperty(ref mProjectNodes_DataContext, value);
}
}
and class ProjectNodesVM has:
public ObservableCollection<ProjectNode> Nodes {
get { return mNodes; }
protected set { SetProperty(ref mNodes, value); }
}
inside ProjectNode class i have:
private string mHeader;
public string Header
{
get { return mHeader; }
set { SetProperty(ref mHeader, value); }
}

I found a simple answer to my specific case, not yours it seems
The children must be a "property".
So:
public ObservableCollection<Tag> ListaFilhos ; //doesn't work
public ObservableCollection<Tag> ListaFilhos {get; set;} //works

WPF - Bind Teeview to List

I have the following task:
create Tree which user can modify through app UI - add new Items, delete existing one. TreeView control should be binded to appropriate List in code behind.
Items in tree are CriteriaItem objects.
public class Subcriteria
{
public Subcriteria(string header)
{
Title = header;
subcriterias = new ObservableCollection<Subcriteria>();
}
public string Title { get; set; }
public ObservableCollection<Subcriteria> subcriterias { get; set; }
}
public class Criteria
{
public Criteria(string header)
{
Title = header;
criterias = new ObservableCollection<Subcriteria>();
}
public string Title { get; set; }
public ObservableCollection<Subcriteria> criterias { get; set; }
}
public MainWindow()
{
InitializeComponent();
public ObservableCollection<Alternative> _alt = new ObservableCollection<Alternative>();
Criteria root = new Criteria("root");
criteriaBundle.Add(root);
trvMenu.DataContext = _alt;
}
XAML:
<TreeView Name="trvMenu" Grid.Row="2" ItemsSource="{Binding criteriaBundle}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding criterias}">
<TextBlock Text="{Binding Title}" />
<HierarchicalDataTemplate.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding subcriterias}">
<TextBlock Text="{Binding Title}" />
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=Title}"/>
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
But it doesn't work. Could you please assist me with binding?

You should change your code-behind like this:
1) You should set DataContext, if you use binding
2) You can use only Properties in binding, not fields
My personal advice that You should read about binding basic and MVVM
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = this;
criteriaBundle = new ObservableCollection<CriteriaItem> {new CriteriaItem("root")};
}
public ObservableCollection<CriteriaItem> criteriaBundle { get; set; }
}
EDIT:

Bind collection to Treeview in WPF

I'm trying to bind a collection to a treeview. My attempt so far have failed.
I miss something despite the articles I read about the matter.
So far I tried the something like, but the Treeview just plot the Id of class A and thats it, with no button to expand.
<Grid>
<TreeView HorizontalAlignment="Left" Height="270" VerticalAlignment="Top" Width="292" ItemsSource="{Binding ManagerObjects}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local:ManagerObject}" ItemsSource="{Binding MyManager}">
<TextBlock Text="{Binding Id}"/>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type local:Manager}" ItemsSource="{Binding ManagerClientServerProperty}">
<TextBlock Text="{Binding ManagerClientServerProperty}"/>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type local1:ManagerClientServer}">
<TextBlock Text="TEST"/>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type local1:NetworkObject}" ItemsSource="{Binding Entities}">
<TextBlock Text="TEST"/>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type local1:RemoteEntity}" ItemsSource="{Binding Fields}">
<TextBlock Text="TEST"/>
<!-- how classD should look like -->
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>
</Grid>
EDIT: ADDING REAL CODE
This is in my Model :
public class ManagerObject
{
// PROPERTIES
public int Id { get; private set; }
public Manager MyManager { get; private set; }
}
public class Manager
{
// FIELDS
private readonly ManagerClientServer managerClientServer;
// PROPERTIES
public ManagerClientServer ManagerClientServerProperty { get { return managerClientServer;} }
/**** OTHER STUFF NON IMPORTANT ****/
}
public class ManagerClientServer
{
// FIELDS
private readonly ObservableCollection<NetworkObject> Clients = new ObservableCollection<NetworkObject>();
private readonly ObservableCollection<NetworkObject> Servers = new ObservableCollection<NetworkObject>();
// PROPERTIES
public ObservableCollection<NetworkObject> ClientsProperty
{
get { return Clients; }
}
public ObservableCollection<NetworkObject> ServersProperty
{
get { return Servers; }
}
/*** OTHER STUFF NON IMPORTANT HERE ***/
}
public class NetworkObject
{
// FIELDS
private readonly ObservableCollection<RemoteEntity> _entities=new ObservableCollection<RemoteEntity>();
public uint NetworkId { get; private set; }
// PROPERTIES
public ObservableCollection<RemoteEntity> Entities
{
get { return _entities; }
}
// CONSTRUCTOR
public NetworkObject(uint id)
{
NetworkId = id;
}
}
public class RemoteEntity
{
// FIELDS
private readonly ObservableCollection<int> _fields=new ObservableCollection<int>();
// PROPERTIES
public bool IsLost { get; set; }
public bool NeedUpdate { get; set; }
public uint SessionId { get; private set; }
public ObservableCollection<int> Fields
{
get { return _fields; }
}
// CONSTRUCTOR
public RemoteEntity(uint id)
{
SessionId = id;
}
}
The ViewModel just expose this property:
public ObservableCollection<ManagerObject> ManagerObjects
{
get { return managerObjects; }
set
{
managerObjects = value;
NotifyOfPropertyChange(()=>ManagerObjects);
}
}
private ObservableCollection<ManagerObject> managerObjects;
The initialization is just 2 ManagerObject, after this they all include a random number of NetworkObjects in both Clients and Servers collection and each of those has a random number of Entities.
All collections here are Observable, however, they are of another type in real but they expose a method which can make them Observable so lets consider it this way.
Many Thanks.

Ah, I see your problem now and it's a really simple one. You can't expand anything because there is nothing to expand. Your TreeView.ItemsSource is bound to the ManagerObjects collection and that's ok, because it is a collection. However, in your HierarchicalDataTemplate for your ManagerObject data type, you have this:
<HierarchicalDataTemplate DataType="{x:Type local:ManagerObject}"
ItemsSource="{Binding MyManager}"> <!-- Look here -->
<TextBlock Text="{Binding Id}"/>
</HierarchicalDataTemplate>
You are trying to data bind the MyManager property to the HierarchicalDataTemplate.ItemsSource property, but you can't because it is not a collection. Instead, try this:
<DataTemplate DataType="{x:Type local:ManagerObject}">
<StackPanel>
<TextBlock Text="{Binding Id}" />
<ContentControl Content="{Binding MyManager}" />
</StackPanel>
</DataTemplate>
You'll have other problems like this too, so you'll have to adjust a number of your templates. For example, this won't work because the ManagerClientServerProperty property is not a collection:
<HierarchicalDataTemplate DataType="{x:Type local:Manager}"
ItemsSource="{Binding ManagerClientServerProperty}">
...
</HierarchicalDataTemplate>
You could do this:
<HierarchicalDataTemplate DataType="{x:Type local:Manager}"
ItemsSource="{Binding ManagerClientServerProperty.Clients}">
...
</HierarchicalDataTemplate>
... but then that would only be one of the collections. When writing WPF, I've learned that it's always best to make your data the right shape to fit your UI. Usually, that just means adding a few extra properties here and there to make your job displaying it easier. For example, instead of using a CompositeCollection in the UI, you could just add an extra property to your ManagerClientServer class. Maybe something like this:
public ObservableCollection<NetworkObject> NetworkObjects
{
get
{
hhh networkObjects = new ObservableCollection<NetworkObject>(Clients);
networkObjects.Add(Servers);
return networkObjects;
}
}
Then you could do this:
<HierarchicalDataTemplate DataType="{x:Type local:Manager}"
ItemsSource="{Binding ManagerClientServerProperty.NetworkObjects}">
...
</HierarchicalDataTemplate>
Anyway, I guess you get the picture now, so I trust that you can finish the rest on your own. Oh, one last thing... don't be surprised if it won't work, because your data is not in the correct 'shape' that a TreeView expects. It might work, but if not, forget the HierarchicalDataTemplates and just define ListBoxes in DataTemplates to bind to the inner collections.

How bind an object to treeview from Xaml

I am trying to bind an object to the treeviewcontrol WPF by XAML, I am getting the treview as empty. When i am doing that by treeview.items.add(GetNode()) then its working.
I am using MVVM Framework(caliburn.Micro) I wanted to do it in Xaml, how do I assign Item source property in xaml? I tried with creating a property of Node class and calling the Method GetNode() with in the property, and assigned that property as itemssource of the treeview and changed the List to Observable collection. Still issue is same.
Working Xaml when doing treeview.items.Add(GetNode()) which returns a Node and and i as assigning Nodes collection to Hireachial Template.
<TreeView Name="treeview2"
Grid.RowSpan="2"
Grid.ColumnSpan="2"
ItemContainerStyle="{StaticResource StretchTreeViewItemStyle}" Width="300">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Nodes}">
<DockPanel LastChildFill="True">
<TextBlock Padding="15,0,30,0" Text="{Binding Path=numitems}" TextAlignment="Right"
DockPanel.Dock="Right"/>
<TextBlock Text="{Binding Path=Text}" DockPanel.Dock="Left" TextAlignment="Left" />
</DockPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
Server Side Code:
this.treeview2.Items.Add(GetNode());
GetNode recursively build a list of type Node.
public class Node
{
public string Text { get; set; }
public List<Node> Nodes { get; set; }
public ObservableCollection<Node> Nodes{get;set;} // with list and observable collection same results
public int numitems { get; set; }
}

In addition to the HierarchicalDataTemplate, which seems just fine, add a binding to the ItemsSource property of your TreeView:
public class ViewModel
{
private List<Node> _rootNodes;
public List<Node> RootNodes
{
get
{
return _rootNodes;
}
set
{
_rootNodes = value;
NotifyPropertyChange(() => RootNodes);
}
}
public ViewModel()
{
RootNodes = new List<Node>{new Node(){Text = "This is a Root Node}",
new Node(){Text = "This is the Second Root Node"}};
}
And in XAML:
<TreeView ItemsSource="{Binding RootNodes}"
.... />
Edit: Remove the call that does this.Treeview.... you don't need that. Try to keep to the minimum the amount of code that references UI Elements. You can do everything with bindings and have no need to manipulate UI Elements in code.

WPF Tree doesn't work

Could you tell me why I can't see subItems?
I've got winforms apps and I added my wpfusercontrol:ObjectsAndZonesTree
ServiceProvider is my webservice. Adn method to get listofcountires with subitems works properly (i get countires, regions from this countires, provinces etc...)
ElementHost elementHost = new ElementHost
{
Width = 150,
Height = 50,
Dock = DockStyle.Fill,
Child = new ObjectsAndZonesTree()
};
this.splitContainer3.Panel1.Controls.Add(elementHost);
XAML:
<TreeView Name="GroupView" Grid.Row="0" Grid.Column="0" ItemsSource="{Binding}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Country
}" ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Region}" >
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Province}" >
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
</TreeView.Resources>
</TreeView>
XAML.CS
public ObjectsAndZonesTree()
{
InitializeComponent();
LoadView();
}
private void LoadView()
{
GroupView.ItemsSource = new ServiceProvider().GetListOfObjectsAndZones();
}
class Country:
public class Country
{
string _name;
[XmlAttribute]
public string Name
{
get { return _name; }
set { _name = value; }
}
string _code;
[XmlAttribute]
public string Code
{
get { return _code; }
set { _code = value; }
}
string _continentCode;
[XmlAttribute]
public string ContinentCode
{
get { return _continentCode; }
set { _continentCode = value; }
}
public Region[] ListOfRegions
{
get { return _listOfRegions; }
set { _listOfRegions = value; }
}
private Region[] _listOfRegions;
public IList<object> Items
{
get
{
IList<object> childNodes = new List<object>();
foreach (var group in this.ListOfRegions)
childNodes.Add(group);
return childNodes;
}
}
}
Class Region:
public class Region
{
private Province[] _listOfProvinces;
private string _name;
private string _code;
public Province[] ListOfProvinces
{
get { return _listOfProvinces; }
set { _listOfProvinces = value; }
}
public string Name
{
get {
return _name;
}
set {
_name = value;
}
}
public string Code
{
get {
return _code;
}
set {
_code = value;
}
}
public string CountryCode
{
get { return _countryCode; }
set { _countryCode = value; }
}
private string _countryCode;
public IList<object> Items
{
get
{
IList<object> childNodes = new List<object>();
foreach (var group in this.ListOfProvinces)
childNodes.Add(group);
return childNodes;
}
}
}
It displays me only list of countires.

Your Region DataTemplate needs to be a HierarchicalDataTemplate to support nested items (SubItems). You also need to specify it's ItemsSource.
<TreeView Name="GroupView" Grid.Row="0" Grid.Column="0" ItemsSource="{Binding}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Country}"
ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Region}"
ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:Province}">
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
</TreeView.Resources>
</TreeView>
So for example if you add Cities to your Provinces the changes in your XAML might look something like this.
<HierarchicalDataTemplate DataType="{x:Type ServiceProvider:Province}"
ItemsSource="{Binding Cities}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
<DataTemplate DataType="{x:Type ServiceProvider:City}">
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>

Not sure where your problem is, but I thought I would share you the best resource I've found when dealing with Treeview. Thoses extension methods saved me a lot of hassle :
http://www.scip.be/index.php?Page=ArticlesNET23
They transform any flat list into a Ienumerable of HierarchyNode using some nice lambda syntax. It is implemented with IQueryable, which means efficient even against a linq datacontext.

Have you implemented INotifyPropertyChanged on Binding source class??
Plus you can check for binding exceptions in output window of visual studio.
It will help you understanding invalid bindings.

You'll need HierarchialDataTemplates instead of plain DataTemplates.
The others wrote everything, so I'll post some useful links:
http://www.codeproject.com/KB/WPF/TreeViewWithViewModel.aspx
http://blogs.msdn.com/mikehillberg/archive/2006/10/11/a-treeview-a-hierarchicaldatatemplate-and-a-2d-collection-walk-into-a-bar.aspx
http://msdn.microsoft.com/en-us/library/system.windows.hierarchicaldatatemplate.aspx