A line which monitors the mouse entering its area

   
  
<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WpfApplication1" Height="352" Width="334" WindowStartupLocation="CenterScreen">
    <StackPanel>
      <Line Name ="SimpleLine" X1 ="0" X2 ="50" Y1 ="0" Y2 ="50" 
            Stroke ="DarkOliveGreen" StrokeThickness ="5"
            ToolTip ="This is a line!" MouseEnter ="SimpleLine_MouseEnter"/>
    </StackPanel>
</Window>
//File:Window.xaml.cs
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;


namespace WpfApplication1
{
  public partial class MainWindow : System.Windows.Window
  {

    public MainWindow()
    {
      InitializeComponent();
    }
    protected void SimpleLine_MouseEnter(object sender, MouseEventArgs args)
    {
      this.Title = String.Format("Mouse entered at: {0}", 
        args.GetPosition(SimpleLine));
    }
  }
}