Change border

   
  
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="AboutDialog" MouseRightButtonDown="AboutDialog_MouseRightButtonDown"
        Title="About WPF Unleashed" SizeToContent="WidthAndHeight"
        Background="OrangeRed">
  <StackPanel>
    <Label FontWeight="Bold" FontSize="20" Foreground="White">
      WPF
    </Label>
    <Label>License</Label>
    <Label>Installed Dll:</Label>
    <ListBox>
      <ListBoxItem>1</ListBoxItem>
      <ListBoxItem>2</ListBoxItem>
      <ListBoxItem>3</ListBoxItem>
      <ListBoxItem>4</ListBoxItem>
      <ListBoxItem>5</ListBoxItem>
      <ListBoxItem>6</ListBoxItem>
      <ListBoxItem>7</ListBoxItem>
      <ListBoxItem>8</ListBoxItem>
      <ListBoxItem>9</ListBoxItem>
      
    </ListBox>
    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
      <Button MinWidth="75" Margin="10">Help</Button>
      <Button MinWidth="75" Margin="10">OK</Button>
    </StackPanel>
    <StatusBar>test</StatusBar>
  </StackPanel>
</Window>
//File:Window.xaml.cs
using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Controls;

public partial class AboutDialog : Window
{
    public AboutDialog()
    {
        InitializeComponent();
    }

    void AboutDialog_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
    {
        Console.WriteLine("Source = " + e.Source.GetType().Name);
        Console.WriteLine("OriginalSource = " + e.OriginalSource.GetType().Name + " @ " + e.Timestamp);
        Control source = e.Source as Control;
        if (source.BorderThickness != new Thickness(5))
        {
            source.BorderThickness = new Thickness(5);
            source.BorderBrush = Brushes.Black;
        }
        else
            source.BorderThickness = new Thickness(0);
    }
}