Question

I have this simple UserControl:

<UserControl x:Class="WPFTreeViewEditing.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>
        <TextBlock Text="Hello, world!" KeyDown="TextBlock_KeyDown" />
    </Grid>
</UserControl>

I want to handle TextBlock.KeyDown event. So, I’ve added an event handler to the code-behind:

public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
    }

    private void TextBlock_KeyDown(object sender, KeyEventArgs e)
    {
        MessageBox.Show("Key up!");
    }
}

but it doesn’t fire. What’s wrong?

UPDATE.

PreviewKeyDown doesn’t fire too.

This UserControl is used in HierarchicalDataTemplate then:

<Window x:Class="WPFTreeViewEditing.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WPFTreeViewEditing"
        Title="MainWindow" Height="265" Width="419">
    <Grid>
        <TreeView ItemsSource="{Binding}">
            <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:ViewModel}" ItemsSource="{Binding Items}">
                    <local:UserControl1 />
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>
    </Grid>
</Window>

Answer 1

From the documentation for UIElement.KeyDown:

Occurs when a key is pressed while focus is on this element.

You’re using TextBlock which doesn’t have the focus, so your KeyDown event will be handled by another control.

You can switch to TextBox and appy some styles so it’ll look and behave like TextBlock, but you’ll be able to get the focus and handle the event.