How do I wrap text in a visual studio modelling diagram shape?

[Merrion]

I have a class that inherits from TextField that is intended to wrap the text across multiple lines.
I replace the standard TextField with it :-

protected override void InitializeShapeFields(IList<ShapeField> shapeFields)
        {
            base.InitializeShapeFields(shapeFields);
            // Find the Comments decorator and make it wrapped
            TextField commentField = FindShapeField(shapeFields, FIELDNAME_DESCRIPTION) as TextField;
            shapeFields.Remove(commentField);
            // Replace with wrapped text field
            UI.Decorators.WrappedTextField   wrappedCommentField = new UI.Decorators.WrappedTextField(commentField);
            shapeFields.Add(wrappedCommentField);
        }

But no wrapping occurs?

The code for WrappedTextField is:

public class WrappedTextField: TextField
    {
 
        public WrappedTextField(TextField prototype)
            : base(prototype.Name )
        {
            // Copy the starting properties form the prototype
            DefaultText = prototype.DefaultText;
            DefaultFocusable = prototype.DefaultFocusable;
            DefaultAutoSize = false;
            DefaultMultipleLine = true;
            AnchoringBehavior.Clear();
            AnchoringBehavior.CenterHorizontally(  );
            AnchoringBehavior.CenterVertically(  ); 
            DefaultAccessibleState = prototype.DefaultAccessibleState;
            
        }
 
    }

Many thanks
Duncan