Data Binding doesn't work in xaml
<p><em>I try to use binding to display Hi in  the Text content.
However, when clicking the button, it doesn't work.
Could someone help me to solve the problem?
Thanks.</em></p>

<p><em>1.XAML CODE :</em></p>

<pre><code>&lt;Window x:Class="Wpftest.binding.Window0"                          
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window0" Height="300" Width="300"&gt;
   &lt;Grid&gt;
      &lt;TextBox x:Name="textBox2" VerticalAlignment="Top" Width="168" 
               Text="{Binding Source= stu,  Path= Name, Mode=TwoWay}"/&gt;
   &lt;/Grid&gt;
&lt;/Window&gt;
</code></pre>

<p><em>2.Class :</em> </p>

<pre><code>namespace Wpftest.binding.Model
{
   public class student : INotifyPropertyChanged 
   {
      public event PropertyChangedEventHandler PropertyChanged;        
      private string name;

      public string Name
      {
         get { return name; }

         set { name = value;

              if(this.PropertyChanged != null)
              {
                 this.PropertyChanged.Invoke(this, new     
                 PropertyChangedEventArgs("Name"));
              }
         }
       }
    }
}
</code></pre>

<p><em>3.XAML.cs:</em> </p>

<pre><code> namespace Wpftest.binding
    {
        public partial class Window0 : Window
        {
            student stu;
            public Window0()
            {
                InitializeComponent();
                stu = new student();
           }

            private void button_Click(object sender, RoutedEventArgs e)
            {
                stu.Name += "Hi!";
            }
        }
    }
</code></pre>