Develop Reference

HierarchicalDataTemplate Binding not working

I want to create a 2 level treview, with the root element of a string "Items":
-Items
-item1
-item2
-...
I have 2 classes to achieve this: ItemList, Item. I call them with the property CurrentItems.
private ItemList _currentItems = null;
public ItemList CurrentItems
{
get
{
return _currentItems;
}
set
{
if(_currentItems!=value)
{
SetProperty(ref _currentItems,
value, () => CurrentItems);
}
}
}
CurrentItems is initialized by creating a temporary ItemsList which is then filled with Items:
ItemList itemTempList = new ItemList();
...
while(...)
{
Item item = new Item();
...
itemTempList.Items.Add(item);
}
CurrentItems = itemTempList;
These are the two classes used:
public class Item
{
public long ObjectID { get; set; }
public string ItemName { get; set; }
}
public class ItemList : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private ObservableCollection<Item> items = new ObservableCollection<Item>();
public ObservableCollection<Item> Items
{
get
{
return items;
}
set
{
items = value;
OnPropertyChanged();
}
}
private ObservableCollection<string> types = new ObservableCollection<string>();
public ObservableCollection<string> Types
{
get
{
if(types.Count > 0)
{
types.Add("Items");
}
return types;
}
set
{
types = value;
OnPropertyChanged();
}
}
protected void OnPropertyChanged([CallerMemberName] string name = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
The View is initialized with a constructor:
public ItemView()
{
InitializeComponent();
}
And finally, this is the xaml:
<TreeView Name="itemTree" Grid.Row="1" Grid.Column="0" SelectedItemChanged="itemTree_SelectedItemChanged"
ItemsSource="{Binding CurrentItems}">
<TreeView.Resources>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="True"/>
</Style>
</TreeView.Resources>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Items,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}">
<Label Content="{Binding Types,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}"/>
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ItemName,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}">
<TextBlock.ContextMenu>
<ContextMenu>
<MenuItem Header="Duplicate" Click="DuplicateCell"/>
<MenuItem Header="Delete" Click="DeleteCell"/>
</ContextMenu>
</TextBlock.ContextMenu>
</TextBlock>
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
With my current understanding and code I am not able to create the TreeView.
Any help would be greatly appreciated!

WPF item selection from user control ListView

I have created a user control with bind able ListView in it. I bind item source and selected item of this control and it works as expected when I use it once in a view. However when I try to reuse the same user control with different item source and selected item, item selection stops working - when I select item from one ListView item from another ListView gets unselected.
I bind my ListView like this:
<ListView
x:Name="SelectionListView"
Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2"
ItemsSource="{Binding ElementName=SelectionListControl, Path=Items}"
Background="Transparent" SelectedItem="{Binding ElementName=SelectionListControl, Path=SelectedItem}">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="6"/>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemTemplate>
<DataTemplate>
<controls:RadioButtonConfig Content="{Binding Text}"
Template="{StaticResource RadioButtonConfig}"
GroupName="DisplayPage"
IsChecked="{Binding IsSelected, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}}"
IsConfigured="{Binding IsConfigured}"/>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Setter Property="Background" Value="Transparent" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListViewItem}">
<ContentPresenter />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListView.ItemContainerStyle>
</ListView>
I added my code to github ListViewBinding project.
Edit:
ListView control code behind:
public partial class SelectionList : UserControl
{
public List<SelectionListItem> Items
{
get { return (List<SelectionListItem>)GetValue(ItemsProperty); }
set { SetValue(ItemsProperty, value); }
}
public static readonly DependencyProperty ItemsProperty =
DependencyProperty.Register("Items", typeof(List<SelectionListItem>), typeof(SelectionList), new PropertyMetadata(new List<SelectionListItem>()));
public SelectionListItem SelectedItem
{
get { return (SelectionListItem)GetValue(SelectedItemProperty); }
set { SetValue(SelectedItemProperty, value); }
}
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register("SelectedItem", typeof(SelectionListItem), typeof(SelectionList), new FrameworkPropertyMetadata(new SelectionListItem(), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
public SelectionList()
{
InitializeComponent();
}
}
ListView Item model (SetProperty raises INotifyPropertyChanged PropertyChanged event):
public class SelectionListItem: ObservableObject
{
private string text;
public string Text
{
get { return text; }
set { SetProperty(ref text, value); }
}
private object valueObj;
public object ValueObj
{
get { return valueObj; }
set { valueObj = value; }
}
private bool isConfigured;
public bool IsConfigured
{
get { return isConfigured; }
set { SetProperty(ref isConfigured, value); }
}
}
I use my controls in MainWindow:
<StackPanel Grid.Row="0">
<local:SelectionList
x:Name="List1"
Items="{Binding SelectableItems}"
SelectedItem="{Binding SelectedItem}"/>
<TextBlock >
<Run Text="Selected Item: "/>
<Run Text="{Binding SelectedItem.Text, FallbackValue=SelectedItem}"/>
</TextBlock>
<TextBlock>
<Run Text="Configured Item: "/>
<Run Text="{Binding ConfiguredItem.Text, FallbackValue=ConfiguredItem}"/>
</TextBlock>
</StackPanel>
<StackPanel Grid.Row="1">
<local:SelectionList
x:Name="List2"
Items="{Binding SelectableItems2}"
SelectedItem="{Binding SelectedItem2}"/>
<TextBlock >
<Run Text="Selected Item: "/>
<Run Text="{Binding SelectedItem2.Text, FallbackValue=SelectedItem}"/>
</TextBlock>
<TextBlock>
<Run Text="Configured Item: "/>
<Run Text="{Binding ConfiguredItem2.Text, FallbackValue=ConfiguredItem}"/>
</TextBlock>
</StackPanel>
With data binded from MainWindowViewModel:
public class MainWindowViewModel : ObservableObject
{
#region list1
private List<SelectionListItem> selectableItems = new List<SelectionListItem>();
public List<SelectionListItem> SelectableItems
{
get { return selectableItems; }
set
{
SelectedItem = value[0];
SetProperty(ref selectableItems, value);
}
}
private SelectionListItem selectedItem = new SelectionListItem { Text = "-", IsConfigured = false };
public SelectionListItem SelectedItem
{
get { return selectedItem; }
set { SetProperty(ref selectedItem, value); }
}
private SelectionListItem configuredItem = new SelectionListItem { Text = "-", IsConfigured = false };
public SelectionListItem ConfiguredItem
{
get { return configuredItem; }
set { SetProperty(ref configuredItem, value); }
}
private string valueText;
public string ValueText
{
get { return valueText; }
set { SetProperty(ref valueText, value); }
}
#endregion
#region list1
private List<SelectionListItem> selectableItems2 = new List<SelectionListItem>();
public List<SelectionListItem> SelectableItems2
{
get { return selectableItems2; }
set
{
SelectedItem2 = value[0];
SetProperty(ref selectableItems2, value);
}
}
private SelectionListItem selectedItem2 = new SelectionListItem { Text = "-", IsConfigured = false };
public SelectionListItem SelectedItem2
{
get { return selectedItem2; }
set { SetProperty(ref selectedItem2, value); }
}
private SelectionListItem configuredItem2 = new SelectionListItem { Text = "-", IsConfigured = false };
public SelectionListItem ConfiguredItem2
{
get { return configuredItem2; }
set { SetProperty(ref configuredItem2, value); }
}
private string valueText2;
public string ValueText2
{
get { return valueText2; }
set { SetProperty(ref valueText2, value); }
}
#endregion
}

How to properly bind multiple ViewModels when using DataTemplateSelector [duplicate]

This question already has answers here:
How to use DataTemplateSelector with ContentControl to display different controls based on the view-model?
(2 answers)
Closed 4 years ago.
I'm trying to write a simple dialog that would accept a value in a SpinEdit or a text in a TextEdit. I'm using multiple VMs and I made a selector that should view a proper control based on the logic in the c++/cli file.
XAML:
xmlns:local="clr-namespace:asd"
Title="{Binding Path=Title, Mode=OneTime}"
<dx:DXWindow.Resources>
<DataTemplate x:Key="TInputValueVM" DataType="{x:Type local:TInputValueVM}">
<dxe:SpinEdit Height="23" Width="200"
Text="{Binding Value, Mode=TwoWay}"
Mask="{Binding Mask, Mode=OneWay}"
MaxLength="{Binding Path=InputLength}" />
</DataTemplate>
<DataTemplate x:Key="TInputTextVM" DataType="{x:Type local:TInputTextVM}">
<dxe:TextEdit Height="23" Width="200"
Text="{Binding Value, Mode=TwoWay}"
MaskType="RegEx" Mask="{Binding Mask, Mode=OneWay}"
MaxLength="{Binding Path=InputLength}"/>
</DataTemplate>
<local:PropertyDataTemplateSelector x:Key="templateSelector"
DataTemplate_Value="{StaticResource TInputValueVM}"
DataTemplate_Text="{StaticResource TInputTextVM}" />
</dx:DXWindow.Resources>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" >
<Label x:Uid="Label" MinHeight="24" MinWidth="60" Content="Value" />
<ContentControl Content="{Binding Path=Whoami}" ContentTemplateSelector="{StaticResource templateSelector}" />
</StackPanel>
<StackPanel Grid.Row="1" x:Uid="OKCancel_Buttons" Orientation="Horizontal" HorizontalAlignment="Right" VerticalAlignment="Bottom">
<Button Height="23" x:Name="OK_Button" Click="OK_Click" Content="OK" IsDefault="True" HorizontalAlignment="Right" MinWidth="95" />
<Button Height="23" x:Name="Cancel_Button" Click="Cancel_Click" Content="Cancel" HorizontalAlignment="Right" MinWidth="95" />
</StackPanel>
</Grid>
In c# I have a base VM and two VMS that extend it, one for values and one for text. The rest of the properties stay the same.
C#
namespace asd
{
public class TInputBaseVM : ViewModelBase
{
private string m_sTitle;
private string m_sMask;
private int m_nInputLenght;
private string m_sWhoami;
public TInputBaseVM(string A_sTitle, string A_sMask, int A_nInputLength)
{
m_sTitle = A_sTitle;
m_sMask = A_sMask;
m_nInputLenght = A_nInputLength;
}
protected string Title
{
get { return m_sTitle; }
set { SetProperty(ref m_sTitle, value, () => Title); }
}
protected string Mask
{
get { return m_sMask; }
set { SetProperty(ref m_sMask, value, () => Mask); }
}
protected int InputLength
{
get { return m_nInputLenght; }
set { SetProperty(ref m_nInputLenght, value, () => InputLength); }
}
protected string Whoami
{
get { return m_sWhoami; }
set { SetProperty(ref m_sWhoami, value, () => Whoami); }
}
}
public class TInputValueVM : TInputBaseVM
{
public TInputValueVM(string A_sTitle, string A_sMask, int A_nInputLength, double A_nValue) : base(A_sTitle, A_sMask, A_nInputLength)
{
Value = A_nValue;
Whoami = "Value";
}
private double m_nValue;
public double Value
{
get { return m_nValue; }
set { SetProperty(ref m_nValue, value, () => Value); }
}
}
public class TInputTextVM : TInputBaseVM
{
public TInputTextVM(string A_sTitle, string A_sMask, int A_nInputLength, string A_sValue) : base(A_sTitle, A_sMask, A_nInputLength)
{
Value = A_sValue;
Whoami = "Text";
}
private string m_sValue;
public string Value
{
get { return m_sValue; }
set { SetProperty(ref m_sValue, value, () => Value); }
}
}
public class PropertyDataTemplateSelector : DataTemplateSelector
{
public DataTemplate DataTemplate_Value { get; set; }
public DataTemplate DataTemplate_Text { get; set; }
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
var selector = item as string;
if(selector == "Value")
return DataTemplate_Value;
return DataTemplate_Text;
}
}
}
In c++/cli I create an object of a proper VM and I'd like the WPF to automatically update the view to either spinedit or textedit, however I'm not sure how to properly bind the properties from the C#. If I explicitly type 'Value' in the Content property of the ContentControl then it displays the spinEdit but I don't know how to bind it so it automatically takes the correct property.
EDIT: I'm adding c++/cli code to show how I choose different VMs
C++/cli:
bool TSignalNumberPositionDialogCLR::StartDialog(TSignalNumberPositionSupport& A_Attributes, HWND A_hwndParent, LPTSTR String)
{
try
{
TInputValueVM ^oExchange_Value;
TInputTextVM ^oExchange_Text;
int inputFormat = A_Attributes.GetInputFormat();
if(inputFormat)
oExchange_Text = gcnew TInputTextVM(gcnew System::String(A_Attributes.GetTitle()), gcnew System::String(A_Attributes.GetMask()),
A_Attributes.GetInputLength(), gcnew System::String(A_Attributes.GetInitialText()));
else
oExchange_Value = gcnew TInputValueVM(gcnew System::String(A_Attributes.GetTitle()), gcnew System::String(A_Attributes.GetMask()),
A_Attributes.GetInputLength(), A_Attributes.GetInitialValue());
Dialogs::TSignalNumberPositionDialog^ dialog = gcnew Dialogs::TSignalNumberPositionDialog();
if(inputFormat)
dialog->DataContext = oExchange_Text;
else
dialog->DataContext = oExchange_Value;
dialog->ShowDialog();
if(dialog->DialogResult)
{
CString nValue;
if(inputFormat)
nValue = oExchange_Text->Value;
else
nValue = ((Decimal)oExchange_Value->Value).ToString("F2", CultureInfo::InvariantCulture);
A_Attributes.UpdateValue(nValue, String, A_Attributes.GetInputLength());
return true;
}
return false;
}
catch(Exception^ e)
{
e;
}
}
based on the 'inputFormat' variable I want to display different controls in the dialog.
EDIT: Based on #Clemens comments I got rid of the selector sectionand the x:Key property in the DataTemplates. I changed the content opf the Content property to Content="{Binding}" and it somehow works. The moment I create a VM it selects the correct one.

Based on your comment. Let me improve my answer. As you are facing issue in VM selection. so plesae concentrate how I assigned VM to datatemplate. Although it is done in very basic way, you can handle it if you you are using MVVM packages.
I have created 2 data template and 2 vms and each vm is bound to datatemplate. To verify, I have a combobox, which will select datatemplate based on selected value.
Here is Sample VM
public class VM : System.ComponentModel.INotifyPropertyChanged
{
private string title;
private SolidColorBrush background;
public string Title { get => title; set { title = value; RaisePropertyChanged(); } }
public SolidColorBrush Background { get => background; set { background = value; RaisePropertyChanged(); } }
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string name = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
public class VM1: VM
{
public VM1()
{
Title = "This is VM1";
Background = Brushes.Yellow;
}
}
public class VM2: VM
{
public VM2()
{
Title = "This is VM2";
Background = Brushes.Orange;
}
}
Now check for resources
<local:VM1 x:Key="VM1"/>
<local:VM2 x:Key="VM2"/>
<DataTemplate x:Key="DT1">
<Grid DataContext="{StaticResource VM1}">
<TextBlock Text="{Binding Title}" Background="{Binding Background}"/>
</Grid>
</DataTemplate>
<DataTemplate x:Key="DT2">
<Grid DataContext="{StaticResource VM2}">
<TextBlock Text="{Binding Title}" Background="{Binding Background}"/>
</Grid>
</DataTemplate>
<Style TargetType="ContentControl" x:Key="contentStyle">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=cmbo, Path=SelectedValue}" Value="Template1">
<Setter Property="ContentTemplate" Value="{StaticResource DT1}" />
</DataTrigger>
<DataTrigger Binding="{Binding ElementName=cmbo, Path=SelectedValue}" Value="Template2">
<Setter Property="ContentTemplate" Value="{StaticResource DT2}" />
</DataTrigger>
</Style.Triggers>
</Style>
and finally I have combobox and content control just to verify
<ComboBox Name="cmbo"/>
<ContentControl Style="{StaticResource contentStyle}"/>
where cmbo.ItemsSource = new List { "Template1", "Template2" };
Hope you got the point

Binding in DataTrigger seems not working

I have a ComboBox which should have a text when nothing is selected. This seems like a straight forward problem, and has many answers on the net, but unfortunately, it is not working for me. I think, the reason is, that I don't want to show a static text, but rather a bound text.
My minimal not working example looks like this:
public class Model
{
public string Name { get; set; }
public SubModel SelectedItem { get; set; }
public List<SubModel> Items { get; set; }
}
public class SubModel
{
public string Description { get; set; }
}
and the MainWindow:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
var selectedSubModel = new SubModel { Description = "SubModel5" };
var model1 = new Model
{
Name = "Model1",
Items = new List<SubModel>
{
new SubModel { Description = "SubModel1" },
new SubModel { Description = "SubModel2" },
new SubModel { Description = "SubModel3" }
}
};
var model2 = new Model
{
Name = "Model2",
SelectedItem = selectedSubModel,
Items = new List<SubModel>
{
new SubModel { Description = "SubModel4" },
selectedSubModel,
new SubModel { Description = "SubModel6" }
}
};
var model3 = new Model
{
Name = "Model3",
Items = new List<SubModel>
{
new SubModel { Description = "SubModel7" },
new SubModel { Description = "SubModel8" },
new SubModel { Description = "SubModel9" }
}
};
_itemsControl.Items.Add(model1);
_itemsControl.Items.Add(model2);
_itemsControl.Items.Add(model3);
}
}
with xaml:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:WpfApplication1="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<ItemsControl x:Name="_itemsControl">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="WpfApplication1:Model">
<ComboBox ItemsSource="{Binding Items}"
SelectedItem="{Binding SelectedItem}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Description}"></TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding SelectedItem}" Value="{x:Null}">
<Setter Property="Background">
<Setter.Value>
<VisualBrush>
<VisualBrush.Visual>
<TextBlock Text="{Binding Name}"/>
</VisualBrush.Visual>
</VisualBrush>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Window>
This gives the follwing:
But it should look similar to this:

please first of all take in your mind facts provided in the next sentence - you can only select items provided by ComboBox ItemsSource. Thus since the Name property values (Model1, Model2, Model3 etc.) are not in your collection they can't be selected you will see the empty selection Instead. I can suggest you the next solution the combination of data context proxy and wpf behavior.
Xaml code
<Window x:Class="ComboBoxWhenNoAnySelectedHelpAttempt.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:comboBoxWhenNoAnySelectedHelpAttempt="clr-namespace:ComboBoxWhenNoAnySelectedHelpAttempt"
xmlns:system="clr-namespace:System;assembly=mscorlib"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ItemsControl x:Name="_itemsControl">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="comboBoxWhenNoAnySelectedHelpAttempt:Model">
<ComboBox x:Name="ComboBox"
SelectedItem="{Binding SelectedItem, UpdateSourceTrigger=PropertyChanged}">
<ComboBox.Resources>
<!--the next object is a proxy that able to provide combo data context each time it requested-->
<comboBoxWhenNoAnySelectedHelpAttempt:FreezableProxyClass x:Key="FreezableProxyClass" ProxiedDataContext="{Binding ElementName=ComboBox, Path=DataContext }"></comboBoxWhenNoAnySelectedHelpAttempt:FreezableProxyClass>
</ComboBox.Resources>
<ComboBox.ItemsSource>
<CompositeCollection>
<!--the next object is a collapsed combo box that can be selected in code-->
<!--keep im mind, since this object is not a SubModel we get the binding expression in output window-->
<ComboBoxItem IsEnabled="False" Visibility="Collapsed" Foreground="Black" Content="{Binding Source={StaticResource FreezableProxyClass},
Path=ProxiedDataContext.Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"></ComboBoxItem>
<CollectionContainer Collection="{Binding Source={StaticResource FreezableProxyClass},
Path=ProxiedDataContext.Items, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</CompositeCollection>
</ComboBox.ItemsSource>
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Description}"></TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
<i:Interaction.Behaviors>
<!--next behavior helps to select a zero index (Model.Name collapsed) item from source when selected item is not SubModel-->
<comboBoxWhenNoAnySelectedHelpAttempt:ComboBoxLoadingBehavior/>
</i:Interaction.Behaviors>
</ComboBox>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
Code Behind with Proxy Code
public class FreezableProxyClass : Freezable
{
protected override Freezable CreateInstanceCore()
{
return new FreezableProxyClass();
}
public static readonly DependencyProperty ProxiedDataContextProperty = DependencyProperty.Register(
"ProxiedDataContext", typeof(object), typeof(FreezableProxyClass), new PropertyMetadata(default(object)));
public object ProxiedDataContext
{
get { return (object)GetValue(ProxiedDataContextProperty); }
set { SetValue(ProxiedDataContextProperty, value); }
}
}
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
var selectedSubModel = new SubModel { Description = "SubModel5" };
var model1 = new Model
{
Name = "Model1",
Items = new ObservableCollection<SubModel>
{
new SubModel { Description = "SubModel1" },
new SubModel { Description = "SubModel2" },
new SubModel { Description = "SubModel3" }
}
};
var model2 = new Model
{
Name = "Model2",
SelectedItem = selectedSubModel,
Items = new ObservableCollection<SubModel>
{
new SubModel { Description = "SubModel4" },
selectedSubModel,
new SubModel { Description = "SubModel6" }
}
};
var model3 = new Model
{
Name = "Model3",
Items = new ObservableCollection<SubModel>
{
new SubModel { Description = "SubModel7" },
new SubModel { Description = "SubModel8" },
new SubModel { Description = "SubModel9" }
}
};
_itemsControl.Items.Add(model1);
_itemsControl.Items.Add(model2);
_itemsControl.Items.Add(model3);
}
}
public class Model:BaseObservableObject
{
private string _name;
private SubModel _selectedItem;
private ObservableCollection<SubModel> _items;
public string Name
{
get { return _name; }
set
{
_name = value;
OnPropertyChanged();
}
}
public SubModel SelectedItem
{
get { return _selectedItem; }
set
{
_selectedItem = value;
OnPropertyChanged();
}
}
public ObservableCollection<SubModel> Items
{
get { return _items; }
set
{
_items = value;
OnPropertyChanged();
}
}
}
public class SubModel:BaseObservableObject
{
private string _description;
public string Description
{
get { return _description; }
set
{
_description = value;
OnPropertyChanged();
}
}
}
BaseObservableObject code (simple implementation for INotifyPropertyChanged )
/// <summary>
/// implements the INotifyPropertyChanged (.net 4.5)
/// </summary>
public class BaseObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
protected virtual void OnPropertyChanged<T>(Expression<Func<T>> raiser)
{
var propName = ((MemberExpression)raiser.Body).Member.Name;
OnPropertyChanged(propName);
}
protected bool Set<T>(ref T field, T value, [CallerMemberName] string name = null)
{
if (!EqualityComparer<T>.Default.Equals(field, value))
{
field = value;
OnPropertyChanged(name);
return true;
}
return false;
}
}
WPF Behavior Code
public class ComboBoxLoadingBehavior:Behavior<ComboBox>
{
private bool _unLoaded;
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.Loaded += AssociatedObjectOnLoaded;
AssociatedObject.LayoutUpdated += AssociatedObjectOnLayoutUpdated;
AssociatedObject.Unloaded += AssociatedObjectOnUnloaded;
}
private void AssociatedObjectOnUnloaded(object sender, RoutedEventArgs routedEventArgs)
{
_unLoaded = true;
UnsubscribeAll();
}
private void UnsubscribeAll()
{
AssociatedObject.Loaded -= AssociatedObjectOnLoaded;
AssociatedObject.LayoutUpdated -= AssociatedObjectOnLayoutUpdated;
AssociatedObject.Unloaded -= AssociatedObjectOnUnloaded;
}
private void AssociatedObjectOnLayoutUpdated(object sender, EventArgs eventArgs)
{
UpdateSelectionState(sender);
}
private static void UpdateSelectionState(object sender)
{
var combo = sender as ComboBox;
if (combo == null) return;
var selectedItem = combo.SelectedItem as SubModel;
if (selectedItem == null)
{
combo.SelectedIndex = 0;
}
}
private void AssociatedObjectOnLoaded(object sender, RoutedEventArgs routedEventArgs)
{
_unLoaded = false;
UpdateSelectionState(sender);
}
protected override void OnDetaching()
{
base.OnDetaching();
if(_unLoaded) return;
UnsubscribeAll();
}
}
This is a working complete solution for you problem, just copy/past and use it as a starting point for your farther research. I'll glad to help if you will have any problems with the code.
Regards.

I've found 2 possible solutions:
Change ComboBox template
Edit standard combobox template by right button click on combobox in designer and select Edit Template -> Edit a Copy...
After that change ContentPresenter with a custom converter:
XAML
<ContentPresenter ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" IsHitTestVisible="false" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<ContentPresenter.Content>
<MultiBinding Converter="{local:ComboboxEmptyValueConverter}">
<Binding Path="SelectionBoxItem" RelativeSource="{RelativeSource Mode=TemplatedParent}" />
<Binding Mode="OneWay" Path="DataContext" RelativeSource="{RelativeSource Mode=TemplatedParent}" />
</MultiBinding>
</ContentPresenter.Content>
</ContentPresenter>
C#
class ComboboxEmptyValueConverterExtension : MarkupExtension, IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
string stringValue = values[0] as string;
var dataContext = values[1] as Model;
return (stringValue != null && String.IsNullOrEmpty(stringValue)) ? dataContext?.Name : values[0];
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
return new object[] { value, null };
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
}
Set ComboBox to IsEditable & IsReadOnly and change Text
<ComboBox ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="textBlock" Text="{Binding Description}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding SelectedItem}" Value="{x:Null}">
<Setter Property="IsEditable" Value="True" />
<Setter Property="IsReadOnly" Value="True" />
<Setter Property="Text" Value="{Binding Name}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>

The answer is, to put the visual brush in the resources of the combobox:
<DataTemplate DataType="WpfApplication1:Model">
<ComboBox ItemsSource="{Binding Items}"
SelectedItem="{Binding SelectedItem}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Description}"></TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
<ComboBox.Resources>
<VisualBrush x:Key="_myBrush">
<VisualBrush.Visual>
<TextBlock Text="{Binding Name}"/>
</VisualBrush.Visual>
</VisualBrush>
</ComboBox.Resources>
<ComboBox.Style>
<Style TargetType="ComboBox">
<Style.Triggers>
<DataTrigger Binding="{Binding SelectedItem}" Value="{x:Null}">
<Setter Property="Background" Value="{StaticResource _myBrush}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>
</DataTemplate>
Then, together with the rest of the code, it works like expected.

ListBox doesn't show any item

I have created a ListBox with custom ListBoxItem Template, had bound everything and it worked. When I was still working on my project. I runned the program and that ListBox weren't showing items anymore. Here is my code:
This is ListBox which doesn't show any item:
<ListBox
x:Name="LB_SongList"
HorizontalAlignment="Left"
Height="498"
Margin="0,30,0,0"
VerticalAlignment="Top"
Width="319"
Background="{x:Null}"
BorderBrush="{x:Null}"
Drop="LB_SongList_Drop"
PreviewMouseMove="LB_SongList_PreviewMouseMove"
PreviewMouseDoubleClick="LB_SongList_PreviewMouseDoubleClick"
SelectionChanged="LB_SongList_SelectionChanged"
AllowDrop="True"
ScrollViewer.HorizontalScrollBarVisibility="Disabled"
ScrollViewer.VerticalScrollBarVisibility="Visible"
SelectionMode="Multiple"
ItemTemplate="{DynamicResource SongTemplate}"/>
Here is my ListBoxItem Template:
<DataTemplate x:Key="SongTemplate">
<Grid Width="302" Height="35">
<Label Content="{Binding SongName}" HorizontalAlignment="Stretch" Margin="4" VerticalAlignment="Stretch" Width="Auto" Height="Auto" Padding="2,0,0,0" VerticalContentAlignment="Center"/>
<Border BorderBrush="#B26A6A6A" BorderThickness="4" HorizontalAlignment="Stretch" Height="35" VerticalAlignment="Top" Width="Auto">
<Border.Style>
<Style>
<Style.Triggers>
<DataTrigger
Binding="{Binding Path=IsSelected, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}}"
Value="False">
<Setter
Property="Border.Visibility"
Value="Collapsed"
/>
</DataTrigger>
</Style.Triggers>
</Style>
</Border.Style>
</Border>
</Grid>
</DataTemplate>
And the code:
public partial class MenuHolder : UserControl
{
private List<string> List_SongList;
public List<string> L_SongList
{
get { return List_SongList; }
set
{
_File.ListToObservableCollection_Song(value, O_SongList);
List_SongList = value;
}
}
public List<string> L_PlayLists
{
get
{
Settings.Default.Save();
return Settings.Default.L_PlayLists;
}
set
{
Settings.Default.L_PlayLists = value;
Settings.Default.Save();
}
}
public ObservableCollection<Song> O_SongList = new ObservableCollection<Song>();
public ObservableCollection<string> O_PlayList = new ObservableCollection<string>();
public MenuHolder()
{
InitializeComponent();
LB_SongList.ItemsSource = O_SongList;
LB_PlayList.ItemsSource = O_PlayList;
List<string> temp = new List<string>();
temp.Add("TestSong");
L_SongList = temp;
}
}
public class Song : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
string _songName;
string _songLengh;
public Song(){}
public Song(String _name){ SongName = _name; }
public Song(String _name, String _lengh) { SongName = _name; SongLengh = _lengh; }
public string SongName
{
get { return _songName; }
set { _songName = value; RaisePropertyChanged("SongName"); }
}
public string SongLengh
{
get { return _songLengh; }
set { _songLengh = value; RaisePropertyChanged("SongLengh"); }
}
private void RaisePropertyChanged(string propertyName)
{
// take a copy to prevent thread issues
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
And the ListToObservableCollection_Song
public void ListToObservableCollection_Song(List<string> _list, ObservableCollection<Music_Player.Menus.MainMenuObjects.Song> _collection)
{
_collection.Clear();
foreach (string _path in _list)
{
_collection.Add(new Menus.MainMenuObjects.Song(GetSongNameFromPath(_path)));
}
}
The worst thing is that it was working before and in the old version of my program it is still working. Still thinking why it is doing that.