Develop Reference

WPF: UserControl with Dependency Property and sub-controls

I'm trying to create my own, very simple, Usercontrol in WPF. It's basically just a Combobox, with some additional Logic in it.
I tried to create my own Depdency-Property using this Tutorial: http://www.codeproject.com/Articles/140620/WPF-Tutorial-Dependency-Property
This is working fine so far, but if the property changes, I'd like to reflect this on the Combobox in the User-Control as well. It seems like I can't bind the subcontrol directly to my new Dependency-Project.
My code is looking like this at the moment:
public partial class ClassSelector : UserControl
{
public static readonly DependencyProperty CurrentValueProperty =
DependencyProperty.Register("CurrentValue", typeof(ClassType),
typeof(ClassSelector), new FrameworkPropertyMetadata());
public ClassType CurrentValue
{
get
{
return (ClassType)this.GetValue(CurrentValueProperty);
}
set
{
this.SetValue(CurrentValueProperty, value);
}
}
public ClassSelector()
{
this.DataContext = this;
InitializeComponent();
cmbClassType.ItemsSource = Enum.GetValues(typeof(ClassType));
}
}
Setting the value of the dependy-property or the Combobox seems weirds to me.
I tried to bind it direclty in the xaml via:
<Grid>
<ComboBox x:Name="cmbClassType" SelectedItem="{Binding Path=CurrentValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectionChanged="cmbClassType_SelectionChanged" />
</Grid>
I tried to map the Dependicy-Project changed Event with the combobox and visa versa, but this leads to very strange code, since the combobox change would have to change the property-value and the property-value the combobox.
I'm quite sure there has to be a possibility to bind a DependencyProperty to a subcontrol, but I can't find a way to make this work.
Thanks in advance for all advices guys and have a nice weekend
Matthias
Edith says: The calling Window needs to bind the Object to the Grid, not to the Window, so for example:
grdMain.DataContext = new DeckSearch();
is working fine, meanwhile
this.DataContext = new DeckSearch();
This behavior is ONLY at my custom control, all other controls worked perfectly fine with the DataContext on the Window itself.

Okay so here I fixed your code and it is working at my end
UserControlCodeBehind
public partial class ClassSelector : UserControl
{
public static readonly DependencyProperty CurrentValueProperty = DependencyProperty.Register("CurrentValue", typeof(ClassType),
typeof(ClassSelector), new FrameworkPropertyMetadata()
{
DefaultValue = ClassType.Type1,
BindsTwoWayByDefault = true,
PropertyChangedCallback = CurrentValueChanged,
DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
});
private static void CurrentValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var obj = (ClassSelector)d;
obj.cmbClassType.SelectedValue = e.NewValue;
}
public ClassType CurrentValue
{
get
{
return (ClassType)this.GetValue(CurrentValueProperty);
}
set
{
this.SetValue(CurrentValueProperty, value);
}
}
public ClassSelector()
{
InitializeComponent();
cmbClassType.ItemsSource = Enum.GetValues(typeof(ClassType));
cmbClassType.SelectedValue = CurrentValue;
}
}
The Xaml part of the UserControl
<Grid>
<ComboBox x:Name="cmbClassType" SelectedValue="{Binding Path=CurrentValue}"/>
</Grid>
Please check if it is working at your end. I have not added any extra code checking for thread safety and all.
EDIT
In my solution I do get my Class Property notification when the CurrentValue changes.
Below is my sample MainWindow Code.
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
DataContext = this;
Task.Run(() =>
{
Thread.Sleep(1000);
Dispatcher.InvokeAsync(() =>
{
customCombobox.CurrentValue = ClassType.Type3;//Updating the UserControl DP
});
Thread.Sleep(2000);
this.CurrentValue = ClassType.Type2;//Updating my local Property
});
}
private ClassType _currentValue;
public ClassType CurrentValue
{
get { return _currentValue; }
set
{
_currentValue = value;
Debug.WriteLine("Value Changed to " + value.ToString());
RaisePropertyChanged("CurrentValue");
}
}
public event PropertyChangedEventHandler PropertyChanged;
void RaisePropertyChanged(string propName)
{
var pc = PropertyChanged;
if (pc != null)
pc(this, new PropertyChangedEventArgs(propName));
}
}
And my MainWindow.xaml
<Window x:Class="WpfApplication.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication"
Title="MainWindow" Height="250" Width="525">
<local:ClassSelector x:Name="customCombobox" Height="25" CurrentValue="{Binding CurrentValue}"/>
</Window>

WPF DataBinding Issues - Possible Noob Problems

I am trying to bind a ViewModel property of type Visibility to the visibility property on a Dock Panel:
Updated ViewModel Code:
public class SelectWaferButtonViewModel : INotifyPropertyChanged
{
private bool isClicked;
public SelectWaferButtonViewModel()
{
isClicked = false;
}
public bool IsControlVisible
{
get
{
return isClicked;
}
set
{
isClicked = value;
OnPropertyChanged("IsControlVisible");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnButtonClick()
{
if (isClicked)
{
IsControlVisible = false;
}
else
{
IsControlVisible = true;
}
}
protected virtual void OnPropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
and here is my updated XAML code:
<DockPanel
Name="tvwDockPanel"
Width="200"
Visibility="{Binding IsControlVisible, FallbackValue=Collapsed, Converter={StaticResource BoolToVisConverter}}"
DockPanel.Dock="Left">
<DockPanel
DockPanel.Dock="Top"
Height="22">
</DockPanel>
and I set the data context in the code behind with this line:
tvwDockPanel.DataContext = btnSelectWaferViewModel;
where btnSelectWaferViewModel is the ViewModel object for this situation.
and for fun, here is my code behind:
public partial class WaferTrackerWindow : Window
{
List<ISubscribeEvents> subscriptionList;
SelectWaferButtonViewModel btnSelectWaferViewModel;
public WaferTrackerWindow()
{
InitializeComponent();
this.InstantiateObjects();
this.SubscribeEvents();
this.SetDataContexts();
}
#region Methods
private void SetDataContexts()
{
tvwDockPanel.DataContext = btnSelectWaferViewModel.IsControlVisible;
}
private void SubscribeEvents()
{
foreach (ISubscribeEvents subscriber in subscriptionList)
{
subscriber.SubscribeEvents();
}
}
private void InstantiateObjects()
{
btnSelectWaferViewModel = new SelectWaferButtonViewModel();
subscriptionList = new List<ISubscribeEvents>();
subscriptionList.Add(
new Classes.WaferTrackerWindow.SelectWaferButtonView(btnSelectWafer, btnSelectWaferViewModel));
}
#endregion
}
All I want to do click the button btnSelectWafer and have the tvwDockPanel's visibility property to get to set to Visible via binding. Then when you click again on btnSelectWafer, tvwDockPanel's visibility property gets set back to Collapsed again. tvwDockPanel's visibility will only ever be either Collapsed or Visible.
Any help would be awesome, I am rather new to this whole data binding concept.

You have several issues here:
First of all, the intent of MVVM (if you're trying to do this with MVVM) is to separate logic from presentation. This means that in no way your ViewModel can have a reference to System.Windows.Controls.Button, nor to System.Windows.Visibility, nor to any other classes inside the System.Windows Namespace.
It is not clear to me what your SelectWaferButtonViewModel class is doing with the Button, but you need to remove the Button from there.
Also, If you need to manipulate the Visibility of a control from the ViewModel layer, you'd better use a Boolean property and the BooleanToVisibilityConverter in XAML:
ViewModel:
public bool IsControlVisible {get;set;} //Don't forget INotifyPropertyChanged!!
XAML:
<Window.Resources>
<BooleanToVisibilityConverter x:Key="BoolToVisConverter"/>
</Window.Resources>
<DockPanel Visibility="{Binding IsControlVisible, Converter={StaticResource BoolToVisConverter}}"/>

The problem is that you're binding your DockPanel to the boolean property of your view model, and then setting the Visiblity property of your UI element to the IsControlVisible property of the datacontext (which doesn't exist).
Change to:
private void SetDataContexts()
{
tvwDockPanel.DataContext = btnSelectWaferViewModel;
}

Making AvalonEdit MVVM compatible

I'm trying to make Avalon MVVM compatible in my WPF application. From googling, I found out that AvalonEdit is not MVVM friendly and I need to export the state of AvalonEdit by making a class derived from TextEditor then adding the necessary dependency properties. I'm afraid that I'm quite lost in Herr Grunwald's answer here:
If you really need to export the state of the editor using MVVM, then I suggest you create a class deriving from TextEditor which adds the necessary dependency properties and synchronizes them with the actual properties in AvalonEdit.
Does anyone have an example or have good suggestions on how to achieve this?

Herr Grunwald is talking about wrapping the TextEditor properties with dependency properties, so that you can bind to them. The basic idea is like this (using the CaretOffset property for example):
Modified TextEditor class
public class MvvmTextEditor : TextEditor, INotifyPropertyChanged
{
public static DependencyProperty CaretOffsetProperty =
DependencyProperty.Register("CaretOffset", typeof(int), typeof(MvvmTextEditor),
// binding changed callback: set value of underlying property
new PropertyMetadata((obj, args) =>
{
MvvmTextEditor target = (MvvmTextEditor)obj;
target.CaretOffset = (int)args.NewValue;
})
);
public new string Text
{
get { return base.Text; }
set { base.Text = value; }
}
public new int CaretOffset
{
get { return base.CaretOffset; }
set { base.CaretOffset = value; }
}
public int Length { get { return base.Text.Length; } }
protected override void OnTextChanged(EventArgs e)
{
RaisePropertyChanged("Length");
base.OnTextChanged(e);
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
}
Now that the CaretOffset has been wrapped in a DependencyProperty, you can bind it to a property, say Offset in your View Model. For illustration, bind a Slider control's value to the same View Model property Offset, and see that when you move the Slider, the Avalon editor's cursor position gets updated:
Test XAML
<Window x:Class="AvalonDemo.TestWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:avalonEdit="http://icsharpcode.net/sharpdevelop/avalonedit"
xmlns:avalonExt="clr-namespace:WpfTest.AvalonExt"
DataContext="{Binding RelativeSource={RelativeSource Self},Path=ViewModel}">
<StackPanel>
<avalonExt:MvvmTextEditor Text="Hello World" CaretOffset="{Binding Offset}" x:Name="editor" />
<Slider Minimum="0" Maximum="{Binding ElementName=editor,Path=Length,Mode=OneWay}"
Value="{Binding Offset}" />
<TextBlock Text="{Binding Path=Offset,StringFormat='Caret Position is {0}'}" />
<TextBlock Text="{Binding Path=Length,ElementName=editor,StringFormat='Length is {0}'}" />
</StackPanel>
</Window>
Test Code-behind
namespace AvalonDemo
{
public partial class TestWindow : Window
{
public AvalonTestModel ViewModel { get; set; }
public TestWindow()
{
ViewModel = new AvalonTestModel();
InitializeComponent();
}
}
}
Test View Model
public class AvalonTestModel : INotifyPropertyChanged
{
private int _offset;
public int Offset
{
get { return _offset; }
set
{
_offset = value;
RaisePropertyChanged("Offset");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
}

You can use the Document property from the editor and bind it to a property of your ViewModel.
Here is the code for the view :
<Window x:Class="AvalonEditIntegration.UI.View"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:AvalonEdit="clr-namespace:ICSharpCode.AvalonEdit;assembly=ICSharpCode.AvalonEdit"
Title="Window1"
WindowStartupLocation="CenterScreen"
Width="500"
Height="500">
<DockPanel>
<Button Content="Show code"
Command="{Binding ShowCode}"
Height="50"
DockPanel.Dock="Bottom" />
<AvalonEdit:TextEditor ShowLineNumbers="True"
Document="{Binding Path=Document}"
FontFamily="Consolas"
FontSize="10pt" />
</DockPanel>
</Window>
And the code for the ViewModel :
namespace AvalonEditIntegration.UI
{
using System.Windows;
using System.Windows.Input;
using ICSharpCode.AvalonEdit.Document;
public class ViewModel
{
public ViewModel()
{
ShowCode = new DelegatingCommand(Show);
Document = new TextDocument();
}
public ICommand ShowCode { get; private set; }
public TextDocument Document { get; set; }
private void Show()
{
MessageBox.Show(Document.Text);
}
}
}
source : blog nawrem.reverse

Not sure if this fits your needs, but I found a way to access all the "important" components of the TextEditor on a ViewModel while having it displayed on a View, still exploring the possibilities though.
What I did was instead of instantiating the TextEditor on the View and then binding the many properties that I will need, I created a Content Control and bound its content to a TextEditor instance that I create in the ViewModel.
View:
<ContentControl Content="{Binding AvalonEditor}" />
ViewModel:
using ICSharpCode.AvalonEdit;
using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Highlighting;
// ...
private TextEditor m_AvalonEditor = new TextEditor();
public TextEditor AvalonEditor => m_AvalonEditor;
Test code in the ViewModel (works!)
// tests with the main component
m_AvalonEditor.SyntaxHighlighting = HighlightingManager.Instance.GetDefinition("XML");
m_AvalonEditor.ShowLineNumbers = true;
m_AvalonEditor.Load(#"C:\testfile.xml");
// test with Options
m_AvalonEditor.Options.HighlightCurrentLine = true;
// test with Text Area
m_AvalonEditor.TextArea.Opacity = 0.5;
// test with Document
m_AvalonEditor.Document.Text += "bla";
At the moment I am still deciding exactly what I need my application to configure/do with the textEditor but from these tests it seems I can change any property from it while keeping a MVVM approach.

How can I bind a background color in WPF/XAML?

What do I have to change to the following code so that the background is red, neither of the 2 ways I tried worked:
(source: deviantsart.com)
XAML:
<Window x:Class="TestBackground88238.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<StackPanel>
<TextBlock Text="{Binding Message}" Background="{Binding Background}"/>
<TextBlock Text="{Binding Message}">
<TextBlock.Background>
<SolidColorBrush Color="{Binding Background}"/>
</TextBlock.Background>
</TextBlock>
</StackPanel>
</Window>
Code Behind:
using System.Windows;
using System.ComponentModel;
namespace TestBackground88238
{
public partial class Window1 : Window, INotifyPropertyChanged
{
#region ViewModelProperty: Background
private string _background;
public string Background
{
get
{
return _background;
}
set
{
_background = value;
OnPropertyChanged("Background");
}
}
#endregion
#region ViewModelProperty: Message
private string _message;
public string Message
{
get
{
return _message;
}
set
{
_message = value;
OnPropertyChanged("Message");
}
}
#endregion
public Window1()
{
InitializeComponent();
DataContext = this;
Background = "Red";
Message = "This is the title, the background should be " + Background + ".";
}
#region INotifiedProperty Block
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
}
Update 1:
I tried Aviad's answer which didn't seem to work. I can do this manually with x:Name as shown here but I want to be able to bind the color to a INotifyPropertyChanged property, how can I do this?
(source: deviantsart.com)
XAML:
<Window x:Class="TestBackground88238.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<StackPanel>
<TextBlock Text="{Binding Message}" Background="{Binding Background}"/>
<TextBlock x:Name="Message2" Text="This one is manually orange."/>
</StackPanel>
</Window>
Code Behind:
using System.Windows;
using System.ComponentModel;
using System.Windows.Media;
namespace TestBackground88238
{
public partial class Window1 : Window, INotifyPropertyChanged
{
#region ViewModelProperty: Background
private Brush _background;
public Brush Background
{
get
{
return _background;
}
set
{
_background = value;
OnPropertyChanged("Background");
}
}
#endregion
#region ViewModelProperty: Message
private string _message;
public string Message
{
get
{
return _message;
}
set
{
_message = value;
OnPropertyChanged("Message");
}
}
#endregion
public Window1()
{
InitializeComponent();
DataContext = this;
Background = new SolidColorBrush(Colors.Red);
Message = "This is the title, the background should be " + Background + ".";
Message2.Background = new SolidColorBrush(Colors.Orange);
}
#region INotifiedProperty Block
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
}

Important:
Make sure you're using System.Windows.Media.Brush and not System.Drawing.Brush
They're not compatible and you'll get binding errors.
The color enumeration you need to use is also different
System.Windows.Media.Colors.Aquamarine (class name is Colors) <--- use this one
System.Drawing.Color.Aquamarine (class name is Color)
If in doubt use Snoop and inspect the element's background property to look for binding errors - or just look in your debug log.

The Background property expects a Brush object, not a string. Change the type of the property to Brush and initialize it thus:
Background = new SolidColorBrush(Colors.Red);

Here you've got a copy-paste code:
class NameToBackgroundConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if(value.ToString() == "System")
{
return new SolidColorBrush(System.Windows.Media.Colors.Aqua);
}else
{
return new SolidColorBrush(System.Windows.Media.Colors.Blue);
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}

I figured this out, it was just a naming conflict issue: if you use TheBackground instead of Background it works as posted in the first example. The property Background was interfering with the Window property background.

I recommend reading the following blog post about debugging data binding: http://beacosta.com/blog/?p=52
And for this concrete issue: If you look at the compiler warnings, you will notice that you property has been hiding the Window.Background property (or Control or whatever class the property defines).

The xaml code:
<Grid x:Name="Message2">
<TextBlock Text="This one is manually orange."/>
</Grid>
The c# code:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
CreateNewColorBrush();
}
private void CreateNewColorBrush()
{
SolidColorBrush my_brush = new SolidColorBrush(Color.FromArgb(255, 255, 215, 0));
Message2.Background = my_brush;
}
This one works in windows 8 store app. Try and see. Good luck !

You assigned a string "Red". Your Background property should be of type Color:
using System.Windows;
using System.ComponentModel;
namespace TestBackground88238
{
public partial class Window1 : Window, INotifyPropertyChanged
{
#region ViewModelProperty: Background
private Color _background;
public Color Background
{
get
{
return _background;
}
set
{
_background = value;
OnPropertyChanged("Background");
}
}
#endregion
//...//
}
Then you can use the binding to the SolidColorBrush like this:
public Window1()
{
InitializeComponent();
DataContext = this;
Background = Colors.Red;
Message = "This is the title, the background should be " + Background.toString() + ".";
}
not 100% sure about the .toString() method on Color-Object. It might tell you it is a Color-Class, but you will figur this out ;)

You can still use "Background" as the property name, as long as you give your window a name and use this name on the "Source" of the Binding.

How to create a UserControl in the MVVM pattern?

Currently, within a real-world application development, I am struggling with the consumption of a custom UserControl in the MVVM pattern.
In my application, there is a DataGrid where the user can select an entry. The DataGrid's SelectedItem is TwoWay-bound to a field of the ViewModel set as DataContext. When the user selects an entry, the field is properly updated (tested). In the Page where holds the DataGrid, the field is bound through XAML to a DependencyProperty of a custom UserControl devised in the MVVM pattern : it bares its own ViewModel which is set as DataContext. The trouble is that the UserControl's DependencyProperty is not updated when the field changes even though the INotifyPropertyChanged interface is correctly implemented (see the comparison with a traditional control in the next minimal working example).
This example is constituted of a Label and bares ViewModelUserControl as a DataContext, UserControl1is consumed by the MainWindow and the binding is compared to that of a Label.
The file MainWindow.xaml:
<Window x:Class="UserControlWithinUserControlDataContext.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Local="clr-namespace:UserControlWithinUserControlDataContext"
Title="MainWindow"
Height="350" Width="525"
>
<StackPanel Orientation="Horizontal"
>
<ListBox SelectedItem="{Binding Text, Mode=TwoWay}"
x:Name="listbox"
Height="150"
>
</ListBox>
<Local:UserControl1 Text="{Binding Text, Mode=OneWay}"
Height="50" Width="150"
/>
<Label Content="{Binding Text, Mode=OneWay}"
/>
</StackPanel>
</Window>
The code-behind MainWindow.xaml.cs:
public partial class MainWindow : Window
{
public ViewModelWindow view_model_window
{
get { return _view_model; }
}
private ViewModelWindow _view_model = new ViewModelWindow();
public MainWindow()
{
InitializeComponent();
DataContext = view_model_window;
IList<String> list = new List<String>();
list.Add("A");
list.Add("B");
list.Add("C");
listbox.ItemsSource = list;
}
}
The ViewModel of the MainWindow, the file ViewModelWindow.cs :
public class ViewModelWindow : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public String Text
{
get { return text; }
set
{
if (text != value)
{
text = value;
NotifyPropertyChanged("Text");
}
}
}
private String text = "Bli";
}
The file UserControl1.xaml:
<UserControl x:Class="UserControlWithinUserControlDataContext.UserControl1"
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">
<Grid>
<Label Content="{Binding Text}"
Background="Magenta"
HorizontalAlignment="Stretch"
/>
</Grid>
</UserControl>
The code-behind file UserControl1.xaml.cs:
public partial class UserControl1 : UserControl
{
public ViewModelUserControl view_model_usercontrol
{
get { return _view_model; }
}
private ViewModelUserControl _view_model = new ViewModelUserControl();
public String Text
{
get { return (String)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(String), typeof(UserControl1),
new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.AffectsRender,
new PropertyChangedCallback(TextPropertyChangedCallback)));
private static void TextPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
UserControl1 user_control = d as UserControl1;
if(user_control != null)
{
user_control.view_model_usercontrol.Text = user_control.Text;
}
}
public UserControl1()
{
InitializeComponent();
DataContext = view_model_usercontrol;
}
}
The ViewModel of UserControl1, the file ViewModelUserControl.cs:
public class ViewModelUserControl : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public String Text
{
get { return text; }
set
{
if (text != value)
{
text = value;
NotifyPropertyChanged("Text");
}
}
}
private String text = "";
}
As you can see when executing this code, the MainWindow's Label gets updated while the UserControl1's Label doesn't.
What am I doing wrong? Is there a way to makes this works?
Many thanks in advance for any clue.

first you do not need to add anything in the UserControl just the XAML. Remove all the code of the UserControl and try.
Let's explain why:
Content="{Binding Text}" you set this in the usercontrol xaml, it's binded to the ViewModelWindow. and that works. and remove in
<Local:UserControl1 => Text="{Binding Text, Mode=OneWay}"
Ok, but it is correct to define a property in the user control in case of other situation?, that's right, in order to do that:
<UserControl x:Name="UserControlInstance"...>
<Label Content="{Binding Text, ElementName=UserControlInstance}" ...>
Where in this case Text is the dependency property and not the datacontext property.
Try the first option, and then the second defining just a Dependency Property and in this case bind the dependency property as you did.
And a tip, if a dependency property is in the visual element tree like in your case you do not need to call the callback.

Thank you Juan for your answer, here is the solution for conceiving the UserControl in the MVVM pattern:
I gave the name root to the Grid of UserControl1 and set its DataContext:
root.DataContext = view_model_usercontrol;
instead of:
DataContext = view_model_usercontrol;
Everything works fine.
Happy ending :)