Question

I am pretty sure I am doing something dreadfully wrong, but can’t figure it out.

I created a simple wrapper around a class and added a dependency property so I could bind to it. However, the binding gives no errors, but does nothing.

In order to simplify things I changed the class to TextBox, and got the same results.

public class TextEditor : TextBox
{
    #region Public Properties

    #region EditorText
    /// <summary>
    /// Gets or sets the text of the editor
    /// </summary>
    public string EditorText
    {
      get
      {
        return (string)GetValue(EditorTextProperty);
      }

      set
      {
        //if (ValidateEditorText(value) == false) return;
        if (EditorText != value)
        {
          SetValue(EditorTextProperty, value);
          base.Text = value;

          //if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("EditorText"));
        }
      }
    }

    public static readonly DependencyProperty EditorTextProperty =
        DependencyProperty.Register("EditorText", typeof(string), typeof(TextEditor));
    #endregion

    #endregion

    #region Constructors

    public TextEditor()
    {
      //Attach to the text changed event
      //TextChanged += new EventHandler(TextEditor_TextChanged);
    }

    #endregion

    #region Event Handlers

    private void TextEditor_TextChanged(object sender, EventArgs e)
    {
      EditorText = base.Text;
    }

    #endregion
}

When I run the following XAML the first gives results, but the second one (EditorText) doesn’t even hit the EditorText property.

<local:TextEditor IsReadOnly="True" Text="{Binding Path=RuleValue, Mode=TwoWay}" WordWrap="True" />
<local:TextEditor IsReadOnly="True" EditorText="{Binding Path=RuleValue, Mode=TwoWay}" WordWrap="True" />

Answer 1

You’re doing extra work in your CLR property. There is no guarantee that your CLR property will be used by WPF so you shouldn’t be doing this. Instead, use metadata on your DP to achieve the same effect.

public string EditorText
{
  get { return (string)GetValue(EditorTextProperty); }
  set { SetValue(EditorTextProperty, value); }
}

public static readonly DependencyProperty EditorTextProperty =
    DependencyProperty.Register(
        "EditorText",
        typeof(string),
        typeof(TextEditor),
        new FrameworkPropertyMetadata(OnEditorTextChanged));

private static void OnEditorTextChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
    var textEditor = dependencyObject as TextEditor;

    // do your extraneous work here
}