为文本块创建事件

Question

I am trying to create a TextChanged Event Handler for a TextBlock using Custom Dependency Property in WindowsstoreApp(WPF),The Event is not getting fired,I dont know where I went wrong,Please guide me ,I have tried so far is,

 public sealed partial class BuyerInput : Page
{       

    public BuyerInput()
    {
        this.InitializeComponent();
        MyTextblock.SetBinding(MyTextProperty, new Binding { Source = MyTextblock.Text,Path = new PropertyPath("MyText") });
    }


    public static readonly DependencyProperty MyTextProperty =   DependencyProperty.Register("MyText", typeof(BuyerInput), typeof(string), new PropertyMetadata(null, OnMyTextChanged));

    public static void OnMyTextChanged(DependencyObject d,  DependencyPropertyChangedEventArgs e)
    {
        //this event is not getting fired whenever the value is changed in TextBlock(MyTextblock)
    }
}

Answer 1

Your DP registration is incorrect . It should be like this:

public static readonly DependencyProperty MyTextProperty =
     DependencyProperty.Register("MyText", typeof(string), typeof(BuyerInput),
           new FrameworkPropertyMetadata
           {
              BindsTwoWayByDefault = true,
              DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged,
              PropertyChangedCallback = OnMyTextChanged
           });

public string MyText
{
   get { return (string)GetValue(MyTextProperty); }
   set { SetValue(MyTextProperty, value); }
}

private static void OnMyTextChanged(DependencyObject d, 
                                        DependencyPropertyChangedEventArgs args)
{
}

Explanation :

• OwneType and DP type parameters are swapped in your registration.
• DP wrappers are missing.
• And make DP to bind TwoWay . Default is OneWay .

---

Binding also is not correct. In case you want to bind to TextBlock name MyTextBlock, it should be:

MyTextblock.SetBinding(TextBlock.TextProperty,
      new Binding { Source = this,Path = new PropertyPath("MyText"), 
                    Mode=BindingMode.TwoWay });

---

Update for comment -

I can't find FrameworkPropertyMetadata in WindowsStoreApp.

In case FrameworkPropertyMetadata is not available on WinRT, use your PropertyMetadata , that will work as well. But you need to set Mode to TwoWay on your binding. I have updated the binding above.