How do you base a style off a built-in control?

Question

In WinUI, I want to create a Decimal NumberBox (like a regular number box, but accepting and returning decimals instead of doubles) and base the style off the existing NumberBox control. How do I do this?

This is what the code behind the control looks like:

public class DecimalBox : NumberBox
{
    public DecimalBox()
    {
        this.DefaultStyleKey = typeof(DecimalBox);
    }

    public new decimal Value
    {
        get { return Convert.ToDecimal(base.Value); }
        set { base.Value = Convert.ToDouble(value); }
    }
}

And this is how I tried to style it:

<Style TargetType="controls:DecimalBox" BasedOn="{StaticResource DefaultNumberBoxStyle}"/>

But I don't know what to put in for the existing DefaultNumberBoxStyle. There is no "DefaultNumberBoxStyle" in the default generic resource dictionary. In the old days, we'd use something like:

<Style TargetType="controls:DecimalBox" BasedOn="{StaticResource {x:Type NumberBox}}"/>

But I don't know what the analog is in WinUI.

Answer 1

If you just want to use the default NumberBox template, you can do it this way:

public sealed class DecimalBox : NumberBox
{
    public DecimalBox()
    {
        this.DefaultStyleKey = typeof(NumberBox);
    }

    public new decimal Value
    {
        get => Convert.ToDecimal(base.Value);
        set => base.Value = Convert.ToDouble(value);
    }
}

If you want to modify the template, you need to bring the entire template from generic.xaml since there's no "DefaultNumberBoxStyle".