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WPF Usercontrol Bindings with MVVM ViewModel not working

I've spent some time trying to solve this problem but couldn't find a solution.
I am trying to bind commands and data inside an user control to my view model. The user control is located inside a window for navigation purposes.
For simplicity I don't want to work with Code-Behind (unless it is unavoidable) and pass all events of the buttons via the ViewModel directly to the controller. Therefore code-behind is unchanged everywhere.
The problem is that any binding I do in the UserControl is ignored.
So the corresponding controller method is never called for the command binding and the data is not displayed in the view for the data binding. And this although the DataContext is set in the controllers.
Interestingly, if I make the view a Window instead of a UserControl and call it initially, everything works.
Does anyone have an idea what the problem could be?
Window.xaml (shortened)
<Window x:Class="Client.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:Client.Views"
mc:Ignorable="d">
<Window.Resources>
<local:SubmoduleSelector x:Key="TemplateSelector" />
</Window.Resources>
<Grid>
<StackPanel>
<Button Command="{Binding OpenUserControlCommand}"/>
</StackPanel>
<ContentControl Content="{Binding ActiveViewModel}" ContentTemplateSelector="{StaticResource TemplateSelector}">
<ContentControl.Resources>
<DataTemplate x:Key="userControlTemplate">
<local:UserControl />
</DataTemplate>
</ContentControl.Resources>
</ContentControl>
</Grid>
</Window>
MainWindowViewModel (shortened)
namespace Client.ViewModels
{
public class MainWindowViewModel : ViewModelBase
{
private ViewModelBase mActiveViewModel;
public ICommand OpenUserControlCommand { get; set; }
public ViewModelBase ActiveViewModel
{
get { return mActiveViewModel; }
set
{
if (mActiveViewModel == value)
return;
mActiveViewModel = value;
OnPropertyChanged("ActiveViewModel");
}
}
}
}
MainWindowController (shortened)
namespace Client.Controllers
{
public class MainWindowController
{
private readonly MainWindow mView;
private readonly MainWindowViewModel mViewModel;
public MainWindowController(MainWindowViewModel mViewModel, MainWindow mView)
{
this.mViewModel = mViewModel;
this.mView = mView;
this.mView.DataContext = mViewModel;
this.mViewModel.OpenUserControlCommand = new RelayCommand(ExecuteOpenUserControlCommand);
}
private void OpenUserControlCommand(object obj)
{
var userControlController = Container.Resolve<UserControlController>(); // Get Controller instance with dependency injection
mViewModel.ActiveViewModel = userControlController.Initialize();
}
}
}
UserControlSub.xaml (shortened)
<UserControl x:Class="Client.Views.UserControlSub"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:Client.Views"
xmlns:viewModels="clr-namespace:Client.ViewModels"
mc:Ignorable="d">
<Grid>
<ListBox ItemsSource="{Binding Models}" SelectedItem="{Binding SelectedModel}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Attr}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<StackPanel>
<Button Command="{Binding Add}">Kategorie hinzufügen</Button>
</StackPanel>
</Grid>
</UserControl>
UserControlViewModel (shortened)
namespace Client.ViewModels
{
public class UserControlViewModel : ViewModelBase
{
private Data _selectedModel;
public ObservableCollection<Data> Models { get; set; } = new ObservableCollection<Data>();
public Data SelectedModel
{
get => _selectedModel;
set
{
if (value == _selectedModel) return;
_selectedModel= value;
OnPropertyChanged("SelectedModel");
}
}
public ICommand Add { get; set; }
}
}
UserControlController (shortened)
namespace Client.Controllers
{
public class UserControlController
{
private readonly UserControlSub mView;
private readonly UserControlViewModel mViewModel;
public UserControlController(UserControlViewModel mViewModel, UserControlSub mView)
{
this.mViewModel = mViewModel;
this.mView = mView;
this.mView.DataContext = mViewModel;
this.mViewModel.Add = new RelayCommand(ExecuteAddCommand);
}
private void ExecuteAddCommand(object obj)
{
Console.WriteLine("This code gets never called!");
}
public override ViewModelBase Initialize()
{
foreach (var mod in server.GetAll())
{
mViewModel.Models.Add(mod);
}
return mViewModel;
}
}
}

WPF Binding and Observable Model fail

In a simple trying-to-learn-WPF experiment I'm trying to bind a property ("InternalName") of an instance of MyModel to the contents of TextBlock "MainWindowTextBlock". Clicking the ``ChangeNameButton" changes the InternalName property of mymodel, but that property change never makes it through to the TextBlock. Nothing happens. What am I doing wrong?
XMAL
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:UserControlExperiments"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<StackPanel Grid.Row ="0">
<Button Width="100" Height="20" Name="ChangeName" Content="Change the Name" Click="ChangeNameButtonClick"/>
<TextBlock Text=""/>
<TextBlock Name="MainWindowTextBox" Width="100" Height="20" Text="{Binding Path = mymodel.InternalName, Mode=TwoWay}"/>
</StackPanel>
</Grid>
</Window>
CODE BEHIND
public partial class MainWindow : Window
{
public MyModel mymodel;
public MainWindow()
{
InitializeComponent();
DataContext = this.DataContext;
mymodel = new MyModel("The old name");
}
private void ChangeNameButtonClick(object sender, RoutedEventArgs e)
{
mymodel.InternalName = "A new name!";
}
}
public class MyModel : INotifyPropertyChanged
{
private string internalname;
public event PropertyChangedEventHandler PropertyChanged;
public MyModel(string nm)
{
InternalName = nm;
}
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public string InternalName
{
get { return internalname; }
set
{
if (internalname != value)
{
internalname = value;
OnPropertyChanged("InternalName");
}
}
}
}
}

The following markup tries to bind to a property named "mymodel" of the current DataContext of the TextBlock, which is inherited from the parent window:
<TextBlock Name="MainWindowTextBox"
Text="{Binding Path = mymodel.InternalName}"/>
So you need to set the DataContext of the window to itself:
DataContext = this;
And you also need to make mymodel a public property since you cannot bind to fields:
public MyModel mymodel { get; }
Then it should work but you probably also want to change the name of the property to comply with the C# naming standards.
You can also remove Mode=TwoWay from the binding. It makes no sense for a TextBlock.

WPF DataGrid not updating with binded BindingList

I have a BindingList binded to a DataGrid, but when I add item to that list, UI is not updating.
Here is a minimal version of code that can reproduce this problem:
MainWindow.xaml
<Window x:Class="WpfTestApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfTestApp1"
mc:Ignorable="d"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<CollectionViewSource x:Key="SessionSource" Source="{Binding Sessions}" />
</Window.Resources>
<Grid>
<DockPanel LastChildFill="True">
<StackPanel DockPanel.Dock="Right">
<Button x:Name="BtnTest" Click="BtnTest_OnClick" Content="Test"></Button>
</StackPanel>
<DataGrid x:Name="DG" DockPanel.Dock="Right" ItemsSource="{Binding Source={StaticResource SessionSource}}">
<DataGrid.Columns>
<DataGridTextColumn x:Name="UserName" Width="Auto" Header="Title" Binding="{Binding Title}"/>
<DataGridTextColumn x:Name="UserAction" Width="Auto" Header="Host" Binding="{Binding Host}"/>
</DataGrid.Columns>
</DataGrid>
</DockPanel>
</Grid>
</Window>
MainWindow.xaml.cs
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;
namespace WpfTestApp1
{
public class Session : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _title;
public string Title { get => _title; set { _title = value; OnPropertyChanged(); } }
private string _host;
public string Host { get => _host; set { _host = value; OnPropertyChanged(); } }
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public partial class MainWindow : Window
{
public BindingList<Session> Sessions { get; set; }
public MainWindow()
{
InitializeComponent();
Sessions = new BindingList<Session>();
}
private void BtnTest_OnClick(object sender, RoutedEventArgs e)
{
Sessions.Add(new Session(){Title = "test1", Host="test2"});
}
}
}
Tried to implement INotifyPropertyChanged interface in MainWindow class, but seems not working too.

Initialize the Sessions property before calling InitializeComponent:
public partial class MainWindow : Window
{
public BindingList<Session> Sessions { get; } = new BindingList<Session>();
public MainWindow()
{
InitializeComponent();
}
private void BtnTest_OnClick(object sender, RoutedEventArgs e)
{
Sessions.Add(new Session { Title = "test1", Host = "test2" });
}
}
In WPF it isn't necessary to use BindingList, especially not when the element type implements INotifyPropertyChanged. ObservableCollection is more common:
public ObservableCollection<Session> Sessions { get; }
= new ObservableCollection<Session>();

Proper databinding in WPF using TabControl and MVVM

Just when I thought I was getting better at this, TabControl is now giving me problems. I have read relevant posts here on StackOverflow, but have been unable to get my simple demo application to work the way I want it to.
To keep things focused, I'll start with a single question about something I don't understand.
I have a TabControl whose TabItems each host the same UserControl. When I set the TabControl.ContentTemplate's DataTemplate to my UserControl, a rendering of that control appears, but it looks like it's the same control for each tab. Or perhaps it's not tied to any of the tabs at all.
MainWindow.xaml
<Window x:Class="TabControlMvvm.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:localviews="clr-namespace:TabControlMvvm.Views"
Title="MainWindow" Height="350" Width="525">
<TabControl ItemsSource="{Binding Tabs}" SelectedIndex="{Binding Selected}">
<TabControl.ContentTemplate>
<DataTemplate>
<localviews:PersonMainPanel />
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
</Window>
Code-behind just sets the ViewModel as its DataContext:
namespace TabControlMvvm {
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window {
public MainWindow()
{
InitializeComponent();
DataContext = new TabControlMvvm.ViewModels.MainViewModel();
}
}
}
The TabItem's Content should be another UserControl, PersonMainPanel.xaml:
<UserControl x:Class="TabControlMvvm.Views.PersonMainPanel"
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:localviews="clr-namespace:TabControlMvvm.Views"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Border BorderBrush="Red" BorderThickness="2">
<TabControl TabStripPlacement="Bottom">
<TabItem Header="Tab 1">
<localviews:MyTabItem />
</TabItem>
<TabItem Header="Tab 2">
<TextBlock Text="This was left blank intentionally" />
</TabItem>
<TabItem Header="Tab 3">
<TextBlock Text="This was also left blank intentionally" />
</TabItem>
</TabControl>
</Border>
</UserControl>
Code-behind:
namespace TabControlMvvm.Views {
/// <summary>
/// Interaction logic for PersonMainPanel.xaml
/// </summary>
public partial class PersonMainPanel : UserControl {
public PersonMainPanel()
{
InitializeComponent();
}
}
}
And the MainViewModel:
namespace TabControlMvvm.ViewModels {
public class MainViewModel : ViewModelBase {
public ICollectionView Tabs { get; set; }
public int Selected { get; set; }
public class Person
{
public string Name { get; set; }
}
public class DummyController {
public List<Person> Persons { get; private set; }
public DummyController()
{
Persons = new List<Person> {
new Person { Name = "Larry" },
new Person { Name = "Darryl" },
new Person { Name = "Other brother Darryl" }
};
}
}
public DummyController Controller { get; private set; }
public RelayCommand HelloCommand { get; set; }
public MainViewModel()
{
Controller = new DummyController();
/*
IEnumerable<TabItem> tabs = Enumerable.Range( 1, _controller.Persons.Count())
.Select( x => new TabItem { Header = String.Format( "Person {0}", x),
Content = new PersonMainPanel() });
*/
IEnumerable<TabItem> tabs = Enumerable.Range( 1, Controller.Persons.Count())
.Select( x => new TabItem { Header = String.Format( "Person {0}", x)});
Tabs = CollectionViewSource.GetDefaultView( tabs.ToList());
Tabs.MoveCurrentToFirst();
InitializeCommands();
}
private void InitializeCommands()
{
HelloCommand = new RelayCommand( () => { MessageBox.Show( String.Format( "Hello, Person {0} named {1}!",
Selected, Controller.Persons[Selected].Name)); });
}
}
}
PersonMainPanel hosts another TabControl, where Tab 1's Content is MyTabItem.xaml:
<UserControl x:Class="TabControlMvvm.Views.MyTabItem"
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"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal">
<TextBlock Text="Name:" />
<TextBox Text="{Binding Name}" Width="100" />
</StackPanel>
<Button Command="{Binding HelloCommand}" Content="Say Hello" />
</StackPanel>
</UserControl>
Code-behind:
namespace TabControlMvvm.Views {
/// <summary>
/// Interaction logic for MyTabItem.xaml
/// </summary>
public partial class MyTabItem : UserControl {
public MyTabItem()
{
InitializeComponent();
}
}
}
Which looks like this at runtime:
Issues I have so far:
When I enter Person 1's Name and then click the Person 2 tab, Person 1's Name is still visible, hence my assumption that the controls are not databound properly. I understand that ItemsControls do not pass their DataContext down to their children, but I am not sure how to fix this without associating the View in code-behind.
I would have expected to get databinding errors in the Output window because of the missing DataContext, but I don't get any errors. I assume the DataContext is null, but wouldn't this still result in a binding error?
How can I use Snoop effectively to debug problems like this?
Here's the sample solution: http://www.filedropper.com/tabcontrolmvvm

Here is solution:
In MainWindow modify your TabControl template, to bind Header from your Model:
<TabControl ItemsSource="{Binding Tabs}" SelectedIndex="{Binding Selected}">
<TabControl.ContentTemplate>
<DataTemplate>
<localviews:PersonMainPanel />
</DataTemplate>
</TabControl.ContentTemplate>
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem">
<Setter Property="Header" Value="{Binding Header}"/>
</Style>
</TabControl.ItemContainerStyle>
</TabControl>
In MyTabItem.xaml, set UpdateTrigger, because default one 'OnLostFocus' can sometimes not save your data:
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" Width="100" />
In MainViewModel modify creating of your tabs, so it will have Name property too:
IEnumerable<TabItem> tabs = Enumerable.Range( 1, Controller.Persons.Count())
.Select( x => new TabItem { Header = String.Format("Person {0}", x), Name = Controller.Persons[x-1].Name });
Also, the most important, create own TabItem class to contain some bounded data:
public class TabItem
{
public string Name { set; get; }
public string Header { set; get; }
}

Specify Binding of DependencyProperty in UserControl itself

Following up on my previous question (Change brushes based on ViewModel property)
In my UserControl I have have a DependencyObject. I want to bind that object to a property of my ViewModel. In this case a CarViewModel, property name is Status and returns an enum value.
public partial class CarView : UserControl
{
public CarStatus Status
{
get { return (CarStatus)GetValue(CarStatusProperty); }
set { SetValue(CarStatusProperty, value); }
}
public static readonly DependencyProperty CarStatusProperty =
DependencyProperty.Register("Status", typeof(CarStatus), typeof(CarView), new PropertyMetadata(OnStatusChanged));
private static void OnStatusChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
var control = (CarView)obj;
control.LoadThemeResources((CarStatus)e.NewValue == CarStatus.Sold);
}
public void LoadThemeResources(bool isSold)
{
// change some brushes
}
}
<UserControl x:Class="MySolution.Views.CarView"
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:views="clr-MySolution.Views"
mc:Ignorable="d"
views:CarView.Status="{Binding Status}">
<UserControl.Resources>
</UserControl.Resources>
<Grid>
<TextBlock Text="{Binding Brand}"FontSize="22" HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
<UserControl
Where do I need to specify this binding? In the root of the UserControl it gives an error:
The attachable property 'Status' was not found in type 'CarView'
In my MainWindow I bind the CarView using a ContentControl:
<ContentControl
Content="{Binding CurrentCar}">
<ContentControl.Resources>
<DataTemplate DataType="{x:Type viewmodel:CarViewModel}">
<views:CarView />
</DataTemplate>
</ContentControl.Resources>
</ContentControl>
My ViewModel:
[ImplementPropertyChanged]
public class CarViewModel
{
public Car Car { get; private set; }
public CarStatus Status
{
get
{
if (_sold) return CarStatus.Sold;
return CarStatus.NotSold;
}
}
}

your binding isn't well written. instead of writing views:CarView.Status="{Binding Status}" you should write only Status="{Binding Status}"

It seems that your Control is binding to itself.
Status is looked for in CarView.
You should have a line of code in your control CodeBehind like :
this.DataContext = new ViewModelObjectWithStatusPropertyToBindFrom();
Regards