twiner Posts - Answer Overflow

twiner

•Created by twiner on 12/22/2022 in #help

❔ Custom DataTemplate for TextElements or alternative approaches

In WPF I'm working on a customized RichTextBox that will add TextElements that are bound to view models. I want to DataTemplates for this, but you can't put TextElements in a DataTemplate. I've been looking into DataTemplate and FrameworkTemplate to see how they work, but its quite involved and maybe I'm over thinking this. I want to be able to supply, in xaml preferably, a collection of mappings between a partially configure DataType and a template that will be bound to it. This is the code I have for the association at the moment, making a copy of the DataContext is easy enough, but I don't know a what to do to make a copy of the ElementTemplate and maintain the binding information.

<x:Array x:Key="DetailTypes" Type="{x:Type v:ContextOption}">
    <v:ContextOption DisplayName="Header">
        <v:ContextOption.DataContext>
            <m:AddDescriptionDetail Style="Header" />
        </v:ContextOption.DataContext>
        <v:ContextOption.ElementTemplate>
            <rt:Header Text="{Binding Path=Description}"/>
        </v:ContextOption.ElementTemplate>
    </v:ContextOption>
</x:Array>

<x:Array x:Key="DetailTypes" Type="{x:Type v:ContextOption}">
    <v:ContextOption DisplayName="Header">
        <v:ContextOption.DataContext>
            <m:AddDescriptionDetail Style="Header" />
        </v:ContextOption.DataContext>
        <v:ContextOption.ElementTemplate>
            <rt:Header Text="{Binding Path=Description}"/>
        </v:ContextOption.ElementTemplate>
    </v:ContextOption>
</x:Array>

    [ContentProperty(nameof(ElementTemplate))]
    public class ContextOption
    {
        public IShallowCloner DataContext { get; set; }
        public string DisplayName { get; set; }
        public TextElement ElementTemplate { get; set; }
    }

    [ContentProperty(nameof(ElementTemplate))]
    public class ContextOption
    {
        public IShallowCloner DataContext { get; set; }
        public string DisplayName { get; set; }
        public TextElement ElementTemplate { get; set; }
    }

4 replies

CC#

•Created by twiner on 12/21/2022 in #help

Sanity check on WPF CustomControl Binding to ViewModel not working

Can someone sanity check me here... In WPF I have a custom control derived from RichTextBox. I needed to have a way to access the selected text from my ViewModel so I could use it to inject into a new object created by said VM However, the value doesn't seem to move across the binding into the view model. So on my view model I made a SelectedText Property

public class MyViewModel : INotifyPropertyChanged {
  public event PropertyChangedEventHandler? PropertyChanged;
  private string _selectedText;
  public string SelectedText { 
    get => _selectedText; 
    set { _selectedText = value; PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedText))); }
  }
}

public class MyViewModel : INotifyPropertyChanged {
  public event PropertyChangedEventHandler? PropertyChanged;
  private string _selectedText;
  public string SelectedText { 
    get => _selectedText; 
    set { _selectedText = value; PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedText))); }
  }
}

and in my custom RichTextBox I have a DependencyProperty

public class AlertTextBox: RichTextBox {
  public static readonly DependencyProperty SelectedTextProperty = DependencyProperty.Register(nameof(SelectedText), typeof(string), typeof(AlertTextBox));
  public string SelectedText
  {
    get => (string)GetValue(SelectedTextProperty);
    set => SetValue(SelectedTextProperty, value);
  }
  public AlertTextBox(){
    Selection.Changed += SelectionChanged;
  }
  public void SelectionChanged(object sender, EventArgs e) => SetCurrentValue(SelectedTextProperty, Selection.Text);
}

public class AlertTextBox: RichTextBox {
  public static readonly DependencyProperty SelectedTextProperty = DependencyProperty.Register(nameof(SelectedText), typeof(string), typeof(AlertTextBox));
  public string SelectedText
  {
    get => (string)GetValue(SelectedTextProperty);
    set => SetValue(SelectedTextProperty, value);
  }
  public AlertTextBox(){
    Selection.Changed += SelectionChanged;
  }
  public void SelectionChanged(object sender, EventArgs e) => SetCurrentValue(SelectedTextProperty, Selection.Text);
}

Finally, in my test Window I have it bound together

   <AlertTextBox SelectedText="{Binding Path=SelectedText}" />

   <AlertTextBox SelectedText="{Binding Path=SelectedText}" />

When inspecting the UI with Snoop, I can see that the binding on SelectedText is considered valid. I believe that using SetCurrentValue is correct to allow the value to propagate across the binding to the ViewModel So I must be missing something, I've done this what feels like countless times and I just don't see what I'm overlooking

10 replies

Gaming

Programming