Routed Events in WPF

<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" Background="Azure">
    <Grid x:Name="grdMain" Height="100" Width="500" HorizontalAlignment="Center"         VerticalAlignment="Center" IsHitTestVisible="True" Background="Black" ToolTip="Grid">
        <Grid.RowDefinitions></Grid.RowDefinitions>
        <StackPanel x:Name="stkMain" Grid.Row="0" Height="80" Width="250"                   IsHitTestVisible="True" Background="Yellow" ToolTip="StackPanel">
            <Button x:Name="btnClick" Content="Click Me" Height="50" Width="90"             Background="Pink" Margin="10" ToolTip="Click Button" IsHitTestVisible="True"/>
        </StackPanel>
    </Grid>
</Window>

using System.Windows;
using System.Windows.Input;
namespace LearningWPF {
    public partial class MainWindow: Window {
        public MainWindow() {
            InitializeComponent();
            grdMain.MouseDown += Grid_MouseDown;
            stkMain.MouseDown += StackPanel_MouseDown;
            btnClick.MouseDown += btnClick_MouseDown;
        }
        void btnClick_Click(object sender, RoutedEventArgs e) {
            MessageBox.Show("Direct Event is getting fired");
        }
        private void btnClick_MouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("Button MouseDown Called");
        }
        private void StackPanel_MouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("StackPanel MouseDown Called");
        }
        private void Grid_MouseDown(object sender, MouseButtonEventArgs e) {
            MessageBox.Show("Grid MouseDown Called");
        }
        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");
        }
    }
}