TextBox KeyDown Trigger Event not working for Backspace and Delete key

Question

I have a Textbox and for that textbox I have attached a keydown event. Everything is working fine but I just noticed that when i'm pressing the 'Backspace' and 'Delete' Key, the binding command is not being called.

My View xaml file :-

<TextBox x:Name="textBox" Width="500" Text="{Binding TextBoxText, UpdateSourceTrigger=PropertyChanged}">
<i:Interaction.Triggers>                
    <i:EventTrigger EventName="KeyDown">  
        <cmd:EventToCommand Command="{BindingPath=TextBoxKeyDownEvent}" PassEventArgsToCommand="True" />                
    </i:EventTrigger>            
</i:Interaction.Triggers>
</TextBox>

My ViewModel cs file :-

    //TextBox Key Down Event Handler
    private DelegateCommand _textBoxKeyDownEvent;
    public ICommand TextBoxKeyDownEvent
    {
        get
        {
            if (_textBoxKeyDownEvent == null)
            {
                _textBoxKeyDownEvent = new DelegateCommand(TextBoxKeyDownEventHandler);
            }
            return _textBoxKeyDownEvent;
        }
        set { }
    }

Can somebody give me some suggestion

Answer 1

EDIT: You have to use PreviewKeyDown the it works. KeyDown is not fired on Space and Delete. If you ignore MVVM and put the handler of KeyDown in codebehind it will also fail.

---

How about binding the Text-Property to a string in you viewmodel?

I build a fast, simple example of my idea.

Result

Text from the TextBox on the left side is simply populated to the Textblock on the right side.

View

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel Orientation="Horizontal">
        <TextBox Text="{Binding TextBoxValue, UpdateSourceTrigger=PropertyChanged}"  Width="250"/>
        <StackPanel Orientation="Horizontal">
            <TextBlock>"</TextBlock>
            <TextBlock Text="{Binding TextBoxValue, UpdateSourceTrigger=PropertyChanged}" />
            <TextBlock>"</TextBlock>
        </StackPanel>
    </StackPanel>
</Window>

ViewModel

public class MainWindowViewModel : INotifyPropertyChanged
{
    private string textBoxValue;

    public string TextBoxValue
    {
        get { return textBoxValue; }
        set
        {
            textBoxValue = value;
            OnTextBoxValueChanged();
            RaisePropertyChanged();
        }
    }

    void OnTextBoxValueChanged()
    {
        // you logic here, if needed.
    }

    #region INotifyPropertyChanged implementation

    public event PropertyChangedEventHandler PropertyChanged;

    void RaisePropertyChanged([CallerMemberName] string propertyName = null)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    #endregion
}