Binding To ICommand From Inside DataTemplate - silverlight

I have a custom control that has an ICommand dependency property. I would like to bind to this property from inside a DataTemplate. To make things clearer here's my code:
DataForm class:
public class DataForm : Form
{
#region Properties
public ICommand HideForm
{
get { return (ICommand)GetValue(HideFormProperty); }
set { SetValue(HideFormProperty, value); }
}
public static readonly DependencyProperty HideFormProperty =
DependencyProperty.Register("HideForm", typeof(ICommand), typeof(DataForm), new PropertyMetadata(null));
#endregion
#region Ctors
public DataForm(Guid formId, String title)
: base(formId, title)
{
this.Template = Application.Current.Resources["DataFormDefaultTemplate"] as ControlTemplate;
}
public DataForm()
: this(Guid.NewGuid(), "bla")
{
}
#endregion
#region Methods
public override void OnApplyTemplate()
{
if (HeaderTemplate == null)
{
HeaderTemplate = Application.Current.Resources["DefaultFormHeaderTemplate"] as DataTemplate;
}
base.OnApplyTemplate();
}
#endregion
}
ControlTemplate of the DataForm:
<ControlTemplate x:Name="DataFormDefaultTemplate" TargetType="my:DataForm">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<ContentPresenter Grid.Row="0" ContentTemplate="{TemplateBinding HeaderTemplate}"></ContentPresenter>
<ContentPresenter Grid.Row="1" ContentTemplate="{TemplateBinding BodyTemplate}"></ContentPresenter>
<ContentPresenter Grid.Row="2" ContentTemplate="{TemplateBinding FooterTemplate}"></ContentPresenter>
</Grid>
</ControlTemplate>
The DataTemplate from which I want to bind to the HideForm command:
<DataTemplate x:Name="DefaultFormHeaderTemplate">
<Grid HorizontalAlignment="Stretch">
<my:TextField FieldViewStyle="{StaticResource formLabelStyle}" Value="Form Title" Mode="View"></my:TextField>
<my:ImageButtonField ImagePath="../Images/Popup_Close.png"
CommandToExecute="{Binding HideForm}"
HorizontalAlignment="Right" Width="8" Height="8"></my:ImageButtonField>
</Grid>
</DataTemplate>
Note: CommandToExecute does work properly on the ImageButtonField. I've already tested it.
Code to instantiate the DataForm:
DataForm form = new DataForm();
form.BodyTemplate = Application.Current.Resources["DataFormBodyTemplate"] as DataTemplate;
form.FooterTemplate = Application.Current.Resources["DataFormFooterTemplate"] as DataTemplate;
form.HideForm = new DelegateCommand(CloseIt);
How do I get this to work? Basically, the perfect scenario is to be able to bind to this command (and other properties) in the data template from the ViewModel without having to add that property (HideForm in this case) to the DataForm class. Shouldn't the DataContext be inherited and - theoretically - what I'm saying should work?

I use EventToCommand in MVVM Light, see example code below.
<UserControl.Resources>
<ContentControl x:Key="ViewModel" Content="{Binding}" />
</UserControl.Resources>
.. Your code here ..
<my:ImageButtonField ImagePath="../Images/Popup_Close.png"
CommandToExecute="{Binding HideForm}"
HorizontalAlignment="Right" Width="8" Height="8">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseLeftButtonUp">
<Command:EventToCommand Command="{Binding Content.YourCommand, Source={StaticResource ViewModel}}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</my:ImageButtonField>
You can read more about EventToCommand <- here.

Turned out that there is no way to get this done with a DataTemplate unless you use a Binding Proxy. The other way around is to use a ControlTemplate instead and bind to the Template property of a ContentControl instead of using a ContentPresenter

Related

wpf Databinding using XAML not working

I am developing a small application for learning purpose. I find that when I bind ItemControl's ItemSource to a ViewModel property in XAML, it doesn't work in an expected way. i.e. It loads the underlying collection with values at the loading time, but any changes to it are not reflected.
However, if I set Itemsource in Codebehind, it works.
When the form is loaded, it shows 2 note objects. Clicking on button should show the 3rd one. I don't understand why setting DataContext using XAML doesn't update to changes in collection. I am sharing snippet of the code here. Any help greatly appreciated.
Cut-down version of XAML -
<Window x:Class="NotesApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:NotesApp"
xmlns:vm="clr-namespace:NotesApp.ViewModel"
Title="MainWindow" Height="480" Width="640">
<Window.DataContext >
<vm:MainViewModel/>
</Window.DataContext>
<DockPanel >
<ScrollViewer VerticalScrollBarVisibility="Auto">
<ItemsControl Name="NoteItemControl" ItemsSource="{Binding notes}" Background="Beige" >
<ItemsControl.LayoutTransform>
<ScaleTransform ScaleX="{Binding Value, ElementName=zoomSlider}" ScaleY="{Binding Value, ElementName=zoomSlider}" />
</ItemsControl.LayoutTransform>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Name="NoteBorder" Background="Green" CornerRadius="3" Margin="5,3,5,3">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<TextBlock Text="{Binding noteText}" Margin="5,3,5,3"/>
<StackPanel Grid.Row="1" Orientation="Vertical" >
<Line X1="0" Y1="0" X2="{Binding ActualWidth,ElementName=NoteBorder}" Y2="0" Stroke="Black" StrokeThickness="1"/>
<TextBlock Text="{Binding Category}" Margin="5,3,5,3"/>
</StackPanel>
</Grid>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</DockPanel>
</Window>
View Code behind-
namespace NotesApp
{
public partial class MainWindow : Window
{
MainViewModel ViewModel { get; set; }
public MainWindow()
{
InitializeComponent();
ViewModel = new MainViewModel();
// IT WORKS IF I BRING IN THIS STATEMENT
//NoteItemControl.ItemsSource = ViewModel.notes;
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
ViewModel.AddNote(new Note("note3", "Category 3"));
}
}
}
ViewModel -
namespace NotesApp.ViewModel
{
public class MainViewModel: INotifyPropertyChanged
{
ObservableCollection<Note> _notes;
public ObservableCollection<Note> notes
{
get
{ return _notes; }
set
{
_notes = value;
OnPropertyChanged("notes");
}
}
public void AddNote(Note note)
{
_notes.Add(note);
OnPropertyChanged("notes");
}
public MainViewModel ()
{
notes = new ObservableCollection<Note>();
notes.Add(new Note("note1", "Category 1"));
notes.Add(new Note("note2", "Category 2"));
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
protected virtual void OnPropertyChanged(string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs( propertyName));
}
}
}
You create a MainViewModel instance and assign it to the MainWindow's DataContext in XAML
<Window.DataContext >
<vm:MainViewModel/>
</Window.DataContext>
The bindings in your XAML use this instance as their source object, as long as you do not explicitly specify some other source. So there is no need (and it's an error) to create another instance in code behind.
Change the MainWindow's constructor like this:
public MainWindow()
{
InitializeComponent();
ViewModel = (MainViewModel)DataContext;
}
Try this :
<Window.Resources>
<vm:MainViewModel x:Key="mainVM"/>
</Window.Resources>
Now use this key as a static resource wherever you bind something like :
<ItemsControl Name="NoteItemControl" ItemsSource="{Binding notes,Source={StaticResource mainVM},Mode=TwoWay}" Background="Beige" >
If you do this, you dont need any datacontext

DependencyProperty in UserControl not binding in ListItem Template

Ok hours of google searching and stakoverflow reading, I have been unable to find the answer to this issue.
I have a UserControl that is used to show a ProgressBar with a DependencyProperty of type double.
The MainPage.XAML.cs contains the DataContext:
void MainPage_Loaded(object sender,RoutedEventArgs e)
{
setDataContext();
MainGameListBox.ItemsSource = vm.GameList;
}
This is whats in the MainPage.XAML:
<ListBox Grid.Row="1" Grid.ColumnSpan="2" x:Name="MainGameListBox"
SelectionChanged="listBoxGameSearch_SelectionChanged" >
<!-- set its ItemsPanel to be a WrapPanel -->
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<toolkit1:WrapPanel />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<toolkit1:ContextMenuService.ContextMenu>
<toolkit1:ContextMenu>
<toolkit1:MenuItem Header="Pin to start" Click="PinGameToStart_Click" />
</toolkit1:ContextMenu>
</toolkit1:ContextMenuService.ContextMenu>
<Grid Width="173" Height="173"
Background="{StaticResource PhoneAccentBrush}" Margin="12">
<Grid.RowDefinitions>
<RowDefinition Height="32"/>
<RowDefinition Height="32"/>
<RowDefinition Height="32"/>
<RowDefinition Height="32"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="86.5"/>
<ColumnDefinition Width="86.5"/>
</Grid.ColumnDefinitions>
<Border Grid.Row="0" Grid.RowSpan="3" Grid.Column="0" Width="64"
Height="64" BorderBrush="#70BC1F" BorderThickness="2"
Margin="6,6,0,0" VerticalAlignment="Top"
HorizontalAlignment="Left">
<Image Source="{Binding GameTile,
Converter={StaticResource imageCacheConverter}}" />
</Border>
<view:CircularProgressChart x:Name="circularProgChart"
Grid.Row="0" Grid.Column="1"
Grid.RowSpan="3" Grid.ColumnSpan="2"
Margin="6"
Loaded="CircularProgressChart_Loaded"
CompletionPercent="{Binding CompletionPercentage}" />
</Grid>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
The CompletionPercent is the DP and the UserControl is below:
public partial class CircularProgressChart:UserControl
{
public double CompletionPercent
{
get { return (double)GetValue(CompletionPercentProperty); }
set { SetValue(CompletionPercentProperty, value); }
}
public static readonly DependencyProperty CompletionPercentProperty = DependencyProperty.Register("CompletionPercent", typeof(double), typeof(CircularProgressChart), new PropertyMetadata(0.0, CompletionPercentChanged));
public CircularProgressChart()
{
try
{
InitializeComponent();
DataContext = this;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
Here's the CompletionPercentage Property:
public class Progress : INotifyPropertyChanged
{
private double _completionPercentage = 0.0;
public double CompletionPercentage
{
get{return _completionPercentage;}
set{
_completionPercentage = value;
NotifyPropertyChanged("CompletionPercentage");
}
}
protected void NotifyPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
Question, is why is the
CompletionPercent="{Binding CompletionPercentage}"
not being bound? It gets the default value 0, but when the CompletionPercentage is updated the DP doesn't get the update. I've checked the NotifyPropertyChanged method and it fires correctly and works in all other parts of code.
The reason is DataContext = this line in CircularProgressChart constructor. {Binding CompletionPercentage} looks for CompletionPercentage property in DataContext, which obviously does not exist in CircularProgressChart. Instance of Progress class never makes it's way to the CircularProgressChart (explicit assignment of dependency property has a priority over binding).
Solution 1 (if you really want to keep dependency property): remove the DataContext = this; line. If you need to bind to properties of CircularProgressChart in it's XAML, specify correct binding sources instead of relying on DataContext.
Solution 2 (very common when deriving from UserControl): remove CompletionPercent dependency property completely (including its binding in MainPage.xaml) and bind to CompletionPercentage directly in CircularProgressChart.xaml. Also remove DataContext = this; line.
Solution 3 (true WPF-way): use default ProgressBar control with a custom template instead of creating your own control.

TemplateBinding to RowDefinition.Height ignored in ContentControl

Description:
I have a custom content control and I am trying to enable some external settings via dependency properties. Basically it's a decorator panel with two grid rows, upper one is the header, the lower one is the content (via ContentPresenter).
There are 3 items that are bound to the template (via TemplateBinding), HeaderHeight, TextSize and Header (each of them has its dependency property of an appropriate type).
Problem:
While two of the bindings work perfectly (even in design-time), the third one does not. The FontSize="{TemplateBinding TextSize}" and the Text="{TemplateBinding Header}" bindings work, but the <RowDefinition Height="{TemplateBinding HeaderHeight}" /> does not work.
The grid splits the rows' heights 50/50, no matter which value I set the HeaderHeight property to. It does not even take the default value from the DP metadata.
Question:
What is the problem with this scenario? Why do the other two bindings work with no problems and this one behaves as if there is no binding at all?
Note:
If I set DataContext = this in the constructor and replace {TemplateBinding HeaderHeight} with {Binding HeaderHeight}, the problem disappears and it works as intended. But I'd like to know why I don't need to do the same thing with other bindings to make them work.
XAML (Themes/Generic.xaml):
<Style TargetType="local:KaiPanel">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="local:KaiPanel">
<Grid x:Name="LayoutRoot">
<Grid.RowDefinitions>
<RowDefinition Height="{TemplateBinding HeaderHeight}" />
<RowDefinition />
</Grid.RowDefinitions>
<Grid Grid.Row="0">
<Border>
<TextBlock FontSize="{TemplateBinding TextSize}"
Text="{TemplateBinding Header}" />
</Border>
</Grid>
<Grid Grid.Row="1">
<Border>
<ContentPresenter />
</Border>
</Grid>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Content Control (C#):
public class KaiPanel : ContentControl
{
public KaiPanel()
{
this.DefaultStyleKey = typeof(KaiPanel);
}
public static readonly DependencyProperty TextSizeProperty =
DependencyProperty.Register("TextSize", typeof(double), typeof(KaiPanel), new PropertyMetadata(15.0));
public double TextSize
{
get { return (double)GetValue(TextSizeProperty); }
set { SetValue(TextSizeProperty, value); }
}
public static readonly DependencyProperty HeaderProperty =
DependencyProperty.Register("Header", typeof(String), typeof(KaiPanel), new PropertyMetadata(""));
public String Header
{
get { return (String)GetValue(HeaderProperty); }
set { SetValue(HeaderProperty, value); }
}
public static readonly DependencyProperty HeaderHeightProperty =
DependencyProperty.Register("HeaderHeight", typeof(GridLength), typeof(KaiPanel), new PropertyMetadata(new GridLength(40)));
public GridLength HeaderHeight
{
get { return (GridLength)GetValue(HeaderHeightProperty); }
set { SetValue(HeaderHeightProperty, value); }
}
}
Custom Control usage (XAML):
<UserControl ...>
<Grid x:Name="LayoutRoot">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150" />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<StackPanel x:Name="buttonsStackPanel" Grid.Column="0" VerticalAlignment="Center">
<!-- Some buttons here -->
</StackPanel>
<Grid Grid.Column="1">
<controls:KaiPanel x:Name="contentPanel">
<navigation:Frame x:Name="contentFrame" Source="KP">
<navigation:Frame.UriMapper>
<uriMapper:UriMapper>
<uriMapper:UriMapping Uri="KP" MappedUri="/Views/Kornelijepetak.xaml" />
<uriMapper:UriMapping Uri="KAI" MappedUri="/Views/KaiNetwork.xaml" />
</uriMapper:UriMapper>
</navigation:Frame.UriMapper>
</navigation:Frame>
</controls:KaiPanel>
</Grid>
</Grid>
</UserControl>
Sadly it seems what you're attempting to do requires more than just a single data binding. RowDefinition isn't a subclass of FrameworkElement, and it doesn't match any of the other criteria specified in the MSDN Silverlight data binding documentation, so it can't be used as the target of a binding.
What you want to do is possible, but unfortunately it involves a little more code.
Firstly, add a field for the main grid (I've called it mainGrid) to your KaiPanel class. Then, override the OnApplyTemplate method in this class to grab the main Grid from the template and keep a reference to it in your mainGrid field:
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
mainGrid = GetTemplateChild("LayoutRoot") as Grid;
SetHeaderRowHeight();
}
This calls a method that updates the height of the first row of the grid. That method is as follows:
private void SetHeaderRowHeight()
{
if (mainGrid != null)
{
mainGrid.RowDefinitions[0].Height = HeaderHeight;
}
}
I admit I'm not 100% sure that OnApplyTemplate is called after the DPs are set. It seems that this is the case (a quick test seemed to confirm this), but all I could find to back this up was this post on the Silverlight forums. If you find that this isn't the case, you'll need to register a PropertyChangedCallback on the HeaderHeight DP that will also call this SetHeaderRowHeight method.
See also http://forums.silverlight.net/forums/t/76992.aspx#183089.
Use RelativeSource and TemplatedParent instead:
<RowDefinition Height="{Binding RelativeSource={RelativeSource TemplatedParent},
Path=HeaderHeight}" />
Here the difference between TemplateBinding and RelativeSource TemplatedParent is explained:
WPF TemplateBinding vs RelativeSource TemplatedParent

MVVM Light Commands within an ItemsControl

I'm just trying my hand at WP7 dev using the MVVM Light framework.
I'm trying to fire a button command inside an ItemsControl, essentialy it's a list of cars and I'd like each element to have an edit button.
The Relevant piece of the View:
<ItemsControl ItemsSource="{Binding MyCars}" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid x:Name="CarViewGrid">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" MinWidth="100" />
<ColumnDefinition Width="Auto" MinWidth="302"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" MinHeight="40" />
<RowDefinition Height="Auto" MinHeight="32" />
<RowDefinition Height="Auto" MinHeight="32" />
<RowDefinition Height="Auto" MinHeight="32" />
</Grid.RowDefinitions>
<TextBlock x:Name="CarName" Text="{Binding Name, Mode=TwoWay}" Margin="7,0" Grid.Row="0" Grid.ColumnSpan="2" FontSize="32" FontWeight="Bold" FontStyle="Normal" />
<TextBlock x:Name="Make" Text="{Binding Make, Mode=TwoWay}" Margin="15,0" Grid.Row="1" Grid.Column="0" FontSize="24" />
<TextBlock x:Name="Model" Text="{Binding Model, Mode=TwoWay}" Grid.Row="1" Grid.Column="1" FontSize="24" />
<TextBlock x:Name="Odometer" Text="{Binding Odometer, Mode=TwoWay}" Margin="15,0" Grid.Row="2" Grid.ColumnSpan="2" FontSize="24" />
<Button x:Name="EditCarButton" Content="Edit" Grid.Row="3" Grid.Column="1" HorizontalAlignment="Right" Width="100" >
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<cmd:EventToCommand Command="{Binding EditCar}" CommandParameter="{Binding}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
My ViewModel contains this:
public RelayCommand OpenNewForm { get; private set; }
public CarViewModel()
{
//Snip
EditCar = new RelayCommand<Car>(c =>
{
CurrentCar = c;
FormVisible = true;
});
}
Now as you can see I'm trying to pass the current Car object that is bound through the CommandParameter. My delegate never fires so I'm guessing I've got something wrong in my binding regarding the current DataContext.
Anybody got any ideas as to what I'm doing wrong?
In a DataTemplate, the DataContext is set by default to the item that is represented by the DataTemplate (in that case, the Car object). If the EditCar command is on the main viewmodel (which also contains the MyCars collection), you need to explicitly set the Source of the Binding to that object. This would be (assuming that you are using the MVVM Light's ViewModelLocator and that your VM is named Main) {Binding Source={StaticResource Locator}, Path=Main.EditCar}
Cheers,
Laurent
Its going to fire EditCar on a car item. There are a couple ways to solve this, since you're using mvvm light try.
Appologies to Laurent. I posted the wrong link. My intention was that since the original poster was using MVVM Light that Dan Wahlin's DataContextProxy or a RelativeSource binding solution would work. I was going to go on and explain how if using CM an event from a child item could bubble up but I didn't. The link to CM dotnetrocks was something I pasted previously.
I have found that its alot easier to make my collections VM collections instead of Entitycollections. I used to use entitycollections and then I started running into those problems like you are describing. But Now each VM in the Collection is 'selfaware' and can act on itself without jumping through major hoops.
You would have the button that you are clicking as part of the CarsVM and it would have access to all the properties of the carVM which would have access to all the properties of your Car Entity.
Sample from My App:
public partial class ReadmitPatientListViewModel : ViewModelBase
{
/// <summary>
/// Initializes a new instance of the ReadmitPatientListViewModel class.
/// </summary>
////public override void Cleanup()
////{
//// // Clean own resources if needed
//// base.Cleanup();
////}
#region Declarations
ICommand _openSurveyCommand;
Messenger _messenger = Messenger.Default;
#endregion
#region Command Properties
public ICommand OpenSurveyCommand
{
get
{
if (_openSurveyCommand == null)
{
_openSurveyCommand = new RelayCommand(() => OnSurveyCommandExecute());
}
return _openSurveyCommand;
}
private set { }
}
#endregion
#region Command Methods
private void OnSurveyCommandExecute()
{
Wait.Begin("Loading Patient List...");
_messenger.Send<ReadmitPatientListViewModel>(this);
_messenger.Send<Messages.NavigationRequest<SubClasses.URI.PageURI>>(GetNavRequest_QUESTIONAIRRESHELL());
}
#endregion
#region Properties
#endregion
private static Messages.NavigationRequest<SubClasses.URI.PageURI> GetNavRequest_QUESTIONAIRRESHELL()
{
Messages.NavigationRequest<SubClasses.URI.PageURI> navRequest =
new Messages.NavigationRequest<SubClasses.URI.PageURI>(
new SubClasses.URI.PageURI(Helpers.PageLinks.QUESTIONAIRRESHELL, System.UriKind.Relative));
return navRequest;
}
partial void OnCreated()
{
}
}
These are the properties in the primary vm that my Expander binds to:
public CollectionViewSource SearchResultsCVS { get; private set; }
public ICollection<ViewModel.ReadmitPatientListViewModel> SearchResults { get; private set; }
The collection is the soure for the CVS.....when the completeSurveyButton is clicked a navigation request is sent,and a copy of the viewmodel is sent to any listeners to manipulate.

How to Implement a ListBox of Checkboxes in WPF?

Although somewhat experienced with writing Winforms applications, the... "vagueness" of WPF still eludes me in terms of best practices and design patterns.
Despite populating my list at runtime, my listbox appears empty.
I have followed the simple instructions from this helpful article to no avail. I suspect that I'm missing some sort of DataBind() method where I tell the listbox that I'm done modifying the underlying list.
In my MainWindow.xaml, I have:
<ListBox ItemsSource="{Binding TopicList}" Height="177" HorizontalAlignment="Left" Margin="15,173,0,0" Name="listTopics" VerticalAlignment="Top" Width="236" Background="#0B000000">
<ListBox.ItemTemplate>
<HierarchicalDataTemplate>
<CheckBox Content="{Binding Name}" IsChecked="{Binding IsChecked}"/>
</HierarchicalDataTemplate>
</ListBox.ItemTemplate>
</ListBox>
In my code-behind, I have:
private void InitializeTopicList( MyDataContext context )
{
List<Topic> topicList = ( from topic in context.Topics select topic ).ToList();
foreach ( Topic topic in topicList )
{
CheckedListItem item = new CheckedListItem();
item.Name = topic.DisplayName;
item.ID = topic.ID;
TopicList.Add( item );
}
}
Which, by tracing through, I know is being populated with four items.
EDIT
I have changed TopicList to an ObservableCollection. It still doesn't work.
public ObservableCollection<CheckedListItem> TopicList;
EDIT #2
I have made two changes that help:
In the .xaml file:
ListBox ItemsSource="{Binding}"
In the source code after I populate the list:
listTopics.DataContext = TopicList;
I'm getting a list, but it's not automagically updating the checkbox states when I refresh those. I suspect a little further reading on my part will resolve this.
Assuming TopicList is not an ObservableCollection<T> therefore when you add items no INotifyCollection changed is being fired to tell the binding engine to update the value.
Change your TopicList to an ObservableCollection<T> which will resolve the current issue. You could also populate the List<T> ahead of time and then the binding will work via OneWay; however ObservableCollection<T> is a more robust approach.
EDIT:
Your TopicList needs to be a property not a member variable; bindings require properties. It does not need to be a DependencyProperty.
EDIT 2:
Modify your ItemTemplate as it does not need to be a HierarchicalDataTemplate
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<CheckBox Content="{Binding Name}" IsChecked="{Binding IsChecked}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
Use ObservableCollection<Topic> instead of List<Topic>
Edit
it implements INotifyCollectionChanged interface to let WPF know when you add/remove/modify items
Edit 2
Since you set TopicList in code, it should be a Dependency Property, not a common field
public ObservableCollection<CheckedListItem> TopicList {
get { return (ObservableCollection<CheckedListItem>)GetValue(TopicListProperty); }
set { SetValue(TopicListProperty, value); }
}
public static readonly DependencyProperty TopicListProperty =
DependencyProperty.Register("TopicList", typeof(ObservableCollection<CheckedListItem>), typeof(MainWindow), new UIPropertyMetadata(null));
Edit 3
To see changes in items
implement INotifyPropertyChanged interface in CheckedListItem (each setter should call PropertyChanged(this, new PropertyChangedEventArgs(<property name as string>)) event)
or derive CheckedListItem from DependencyObject, and convert Name, ID, IsChecked to dependency properties
or update them totally (topicList[0] = new CheckedListItem() { Name = ..., ID = ... })
First you dont need a HeirarchicalDataTemplate for this. Just regular DataTemplate as Aaron has given is enough.
Then you need to instantiate the TopicList ObservableCollection somewhere inside the constructor of the class. which makes the ObservableCollection alive even before you add data in to it And binding system knows the collection. Then when you add each and every Topic/CheckedListItem it will automatically shows up in the UI.
TopicList = new ObservableCollection<CheckedListItem>(); //This should happen only once
private void InitializeTopicList( MyDataContext context )
{
TopicList.Clear();
foreach ( Topic topic in topicList )
{
CheckedListItem item = new CheckedListItem();
item.Name = topic.DisplayName;
item.ID = topic.ID;
TopicList.Add( item );
}
}
Others have already made useful suggestions (use an observable collection to get list-change notification, make the collection a property rather than a field). Here are two they haven't:
1) Whenever you're having a problem with data binding, look in the Output window to make sure that you're not getting any binding errors. You can spend a lot of time trying to fix the wrong problem if you don't do this.
2) Understand the role change notification plays in binding. Changes in your data source can't and won't get propagated to the UI unless the data source implements change notification. There are two ways to do this for normal properties: make the data source derive from DependencyObject and make the bound property a dependency property, or make the data source implement INotifyPropertyChanged and raise the PropertyChanged event when the property's value changes. When binding an ItemsControl to a collection, use a collection class that implements INotifyCollectionChanged (like ObservableCollection<T>), so that changes to the contents and order of the collection will get propagated to the bound control. (Note that if you want changes to the items in the collection to get propagated to the bound controls, those items need to implement change notification too.)
I know this is really old question but I came to building custom Listbox which get the SelectedItems with built in select all / unselect all
CustomListBox
public class CustomListBox : ListBox
{
#region Constants
public static new readonly DependencyProperty SelectedItemsProperty = DependencyProperty.Register(nameof(SelectedItems), typeof(IList), typeof(CustomListBox), new PropertyMetadata(default(IList), OnSelectedItemsPropertyChanged));
#endregion
#region Properties
public new IList SelectedItems
{
get => (IList)GetValue(SelectedItemsProperty);
set => SetValue(SelectedItemsProperty, value);
}
#endregion
#region Event Handlers
private static void OnSelectedItemsPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((CustomListBox)d).OnSelectedItemsChanged((IList)e.OldValue, (IList)e.NewValue);
}
protected virtual void OnSelectedItemsChanged(IList oldSelectedItems, IList newSelectedItems)
{
}
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
base.OnSelectionChanged(e);
SetValue(SelectedItemsProperty, base.SelectedItems);
}
#endregion
}
ListBoxControl.cs
public partial class ListBoxControl : UserControl
{
#region Constants
public static new readonly DependencyProperty ContentProperty =
DependencyProperty.Register(nameof(Content), typeof(object), typeof(ListBoxControl),
new PropertyMetadata(null));
public static new readonly DependencyProperty ContentTemplateProperty =
DependencyProperty.Register(nameof(ContentTemplate), typeof(DataTemplate), typeof(ListBoxControl),
new PropertyMetadata(null));
public static readonly DependencyProperty ItemsProperty =
DependencyProperty.Register(nameof(Items), typeof(IList), typeof(ListBoxControl),
new PropertyMetadata(null));
public static readonly DependencyProperty SelectedItemsProperty =
DependencyProperty.Register(nameof(SelectedItems), typeof(IList), typeof(ListBoxControl),
new UIPropertyMetadata(null, OnSelectedItemsChanged));
#endregion
#region Properties
public new DataTemplate ContentTemplate
{
get => (DataTemplate)GetValue(ContentTemplateProperty);
set => SetValue(ContentTemplateProperty, value);
}
public IList Items
{
get => (IList)GetValue(ItemsProperty);
set => SetValue(ItemsProperty, value);
}
public IList SelectedItems
{
get => (IList)GetValue(SelectedItemsProperty);
set => SetValue(SelectedItemsProperty, value);
}
#endregion
#region Constructors
public ListBoxControl()
{
InitializeComponent();
}
#endregion
#region Event Handlers
private static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is not ListBoxControl || e.NewValue is not IList newValue)
{
return;
}
var mylist = (d as ListBoxControl).CustomList;
foreach (var selectedItem in newValue)
{
mylist.UpdateLayout();
if (mylist.ItemContainerGenerator.ContainerFromItem(selectedItem) is ListBoxItem selectedListBoxItem)
{
selectedListBoxItem.IsSelected = true;
}
}
}
#endregion
#region Private Methods
private void CheckAll_Click(object sender, RoutedEventArgs e)
{
CustomList.SelectAll();
}
private void UncheckAll_Click(object sender, RoutedEventArgs e)
{
CustomList.UnselectAll();
}
#endregion
}
#endregion
ListBoxControl.xaml
<UserControl x:Class="UserControls.ListBoxControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:UserControls"
xmlns:str="Client.Properties"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800"
x:Name="this">
<UserControl.Resources>
<BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
</UserControl.Resources>
<Grid >
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<local:CustomListBox x:Name="CustomList"
Grid.Row="0"
Width="250"
HorizontalAlignment="Left"
SelectionMode="Multiple"
Visibility="Visible"
MinHeight="25"
MaxHeight="400"
ItemsSource="{Binding ElementName=this, Path =Items}"
SelectedItems="{Binding ElementName=this, Path =SelectedItems,Mode=TwoWay}"
Style="{StaticResource {x:Type ListBox}}"
ScrollViewer.VerticalScrollBarVisibility="Auto">
<local:CustomListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True" >
<Setter Property="FontWeight" Value="Bold" />
<Setter Property="Background" Value="Transparent" />
<Setter Property="BorderThickness" Value="0" />
</Trigger>
<Trigger Property="IsMouseCaptureWithin" Value="true">
<Setter Property="IsSelected" Value="true" />
</Trigger>
<Trigger Property="IsMouseCaptureWithin" Value="False">
<Setter Property="IsSelected" Value="False" />
</Trigger>
</Style.Triggers>
</Style>
</local:CustomListBox.ItemContainerStyle>
<local:CustomListBox.ItemTemplate>
<DataTemplate>
<DockPanel>
<CheckBox Margin="4" IsChecked="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}},Path=IsSelected}" />
<ContentPresenter Content="{Binding .}" ContentTemplate="{Binding ElementName=this, Path = ContentTemplate, Mode=OneWay}"/>
</DockPanel>
</DataTemplate>
</local:CustomListBox.ItemTemplate>
</local:CustomListBox>
<Grid Grid.Row="1" Grid.Column="1" HorizontalAlignment="Stretch" >
<Grid.RowDefinitions>
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="250" />
</Grid.ColumnDefinitions>
<StackPanel Grid.Row="0" Grid.Column="1"
Orientation="Horizontal"
HorizontalAlignment="Left">
<Button Click="CheckAll_Click"
BorderBrush="Transparent"
ToolTip="Check all">
<Button.Content>
<Image Source="CheckAll.png" Height="16" Width="16"/>
</Button.Content>
</Button>
<Button
Click="UncheckAll_Click"
BorderBrush="Transparent"
Visibility="Visible"
ToolTip="Unchecked all">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=this, Path = SelectedItems.Count}" Value="0">
<Setter Property="Button.Visibility" Value="Collapsed" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
<Button.Content>
<Image Source="UncheckAll.png" Height="16" Width="16" />
</Button.Content>
</Button>
</StackPanel>
<TextBlock Grid.Row="0" Grid.Column="1"
Text="{Binding ElementName=this, Path = SelectedItems.Count, StringFormat={x:Static str:Resources.STE_LABEL_X_ITEMS_CHECKED}, Mode=OneWay}"
HorizontalAlignment="Right" TextAlignment="Right" VerticalAlignment="Center"
Foreground="White" />
</Grid>
</Grid>
</UserControl>
Now you can use that custom control in any control or page and pass any content you want
EX : ConfigView.xaml
<UserControl ..
xmlns:userControls="Client.UserControls"
..>
<userControls:ListBoxControl
ShowCheckBox="True"
MinHeight="25"
MaxHeight="400"
ScrollViewer.VerticalScrollBarVisibility="Auto"
Items="{Binding MyLists, Mode=OneWay}"
SelectedItems="{Binding SelectedMyLists,Mode=TwoWay}"
HorizontalAlignment="Left">
<userControls:ListBoxControl.ContentTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" >
<Image Source="{Binding Icon}"/>
<TextBlock VerticalAlignment="Center" Text="{Binding Name,StringFormat=' {0}'}" />
</StackPanel>
</DataTemplate>
</userControls:ListBoxControl.ContentTemplate>
</userControls:ListBoxControl>
here we bind to the selected items and than do explicit casting to our model
ConfigViewViewModel
private IList _myLists;
public IList MyLists
{
get => _myLists;
set
{
if (_myLists == value)
{
return;
}
_myLists = value;
OnPropertyChanged(nameof(SelectedItems));
}
}
public IEnumerable<MyModel> SelectedItems => MyLists.Cast<MyModel>();
change your binding to
<ListBox ItemsSource="{Binding Path=TopicList}"

Resources