Hiding a Dependency Property - wpf

Question

Just wondering if this is a good practice or if it could cause any troubles in the long run. To be honest, I'm surprised it even works - it does the job, but I'm not sure if it's risky.
Basically we created a NumericTextBox that derives from TextBox, and we overrode the Text property with the new keyword to remove commas from the text:
public class NumericTextBox : TextBox
{
public new string Text
{
get
{
return base.Text.Replace(",", String.Empty);
}
set
{
base.Text = value;
}
}
}
What I don't like about it is that I know Text is a dependency property and we're overriding it, but surprisingly we can still bind to it in XAML:
<this:NumericTextBox x:Name="textBox"
Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}, Path=SomeText, Converter={StaticResource debugConverter}}" />
Then in C# when we call textBox.Text we do get the values without commas.
What do you guys think?

Answer 1

Perhaps you should add your class as an owner of the dependency property and override the getter and setter there:
public class NumericTextBox : TextBox
{
public NumericTextBox() { }
public static readonly DependencyProperty NumericTextProperty = TextBox.TextProperty.AddOwner(typeof(NumericTextBox), new PropertyMetadata(null));
public new string Text
{
get { return ((string)this.GetValue(NumericTextProperty )).Replace(",", String.Empty); }
set { this.SetValue(NumericTextProperty , value); }
}
}
You also have the possibility of overriding the metadata of the dependency property to hook in a custom validation callback method.
You approach doesn't work, because WPF doesn't actually use the class properties to change the value, but the dependency property system. It simply calls the SetValue method as you do in your property setter. You can try it out by setting a breakpoint in the setter, and changing the bound property in the gui. The setter breakpoint will never be hit. But you can hook into the events provided by the dependency property metadata.