title: How to correct bind property to textbox?
body: <p>I write these code in mainpage.xaml</p>
  
  <pre><code>&lt;Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"&gt;
          &lt;StackPanel&gt;
              &lt;TextBox x:Name="xxx" Text="{Binding Test}" TextChanged="xxx_TextChanged" /&gt;
              &lt;Button x:Name="click" Click="click_Click" Content="click" /&gt;
          &lt;/StackPanel&gt;
      &lt;/Grid&gt;
  </code></pre>
  
  <p>And these in mainpage.xaml.cs</p>
  
  <pre><code>  private string test;
      public string Test
      {
          get { return test; }
          set 
          {
              if (test != value)
              {
                  test = value;
                  OnPropertyChanged("Test");
              }
          }
      }
  
      public event PropertyChangedEventHandler PropertyChanged;
  
      public  void OnPropertyChanged(string PropertyName)
      {
          if (PropertyChanged != null)
          {
              PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
          }
      }
  
      // Constructor
      public MainPage()
      {
          InitializeComponent();
      }
  
      private void xxx_TextChanged(object sender, TextChangedEventArgs e)
      {
          Debug.WriteLine(Test);
          Debug.WriteLine(test);
      }
  </code></pre>
  
  <p>But Test isn't binded to textbox, when I write smth to textbox Test isn't changed.
  What I doing wrong and how to correct that ?</p>