WPF TextBox TextProperty metadata override

Question

How to override the TextProperty Metadata to set the UpdateSourceTrigger.PropertyChanged by default while using the functionality from the base TextBox Class

TextBox.OnTextPropertyChanged
TextBox.CoerceText

methods, when both mentioned are private ?

public class MyTextBox : System.Windows.Controls.TextBox
    {
        static MyTextBox()
        {

TextProperty.OverrideMetadata(typeof(TextBox), new FrameworkPropertyMetadata(
                string.Empty, FrameworkPropertyMetadataOptions.Journal | FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, 
                new PropertyChangedCallback(TextBox.OnTextPropertyChanged), 
                new CoerceValueCallback(TextBox.CoerceText), true, UpdateSourceTrigger.PropertyChanged));
...

Answer 1

You should be able to use the GetDefaultMetadata method which will give you access to the callbacks that refer to the private methods.

The following worked for me:

public class MyTextBox : TextBox
{
    static MyTextBox()
    {
        var defaultMetadata = TextBox.TextProperty.GetMetadata(typeof(TextBox));

        TextBox.TextProperty.OverrideMetadata(typeof(MyTextBox), new FrameworkPropertyMetadata(
            string.Empty, FrameworkPropertyMetadataOptions.Journal | FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
            defaultMetadata.PropertyChangedCallback,
            defaultMetadata.CoerceValueCallback, 
            true, 
            System.Windows.Data.UpdateSourceTrigger.PropertyChanged)); 
    }
}