Understanding of Tunnelling Concept in WPF

Here we will be use preview mouse down event for all the possible control and will check that how event is getting raised.

<Window x:Class="LearningWPF.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">
    <Grid Height="100" Width="500" HorizontalAlignment="Center" VerticalAlignment="Center" PreviewMouseDown="Grid_PreviewMouseDown">
        <Grid.RowDefinitions></Grid.RowDefinitions>
        <StackPanel Grid.Row="0" PreviewMouseDown="StackPanel_PreviewMouseDown">
            <Button x:Name="btnClick" Content="Click Me" Height="50" Width="90" PreviewMouseDown="btnClick_PreviewMouseDown"/>
        </StackPanel>
    </Grid>
</Window>

using System.Windows;
using System.Windows.Input;
namespace LearningWPF {
    public partial class MainWindow: Window {
        public MainWindow() {
            InitializeComponent();
        }
        private void Grid_PreviewMouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("Grid Preview MouseDown Called");
        }
        private void StackPanel_PreviewMouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("StackPanel Preview MouseDown Called");
        }
        private void btnClick_PreviewMouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("Button Preview MouseDown Called");
        }
    }
}