Hexadecimal not initialized correctly

[Justin113D]

If a NumericBox<T> has the NumberStyle HexNumber, and the bound property has a default value other than 0, the initial text is not being parsed correctly.

Example code:

Viewmodel.cs

namespace NumericIssue
{
    public class Viewmodel : INotifyPropertyChanged
    {
        private int _hexValue = 0xBEEF;

        public int HexValue
        {
            get => _hexValue;
            set
            {
                _hexValue = value;
                PropertyChanged.Invoke(this, 
                    new PropertyChangedEventArgs(nameof(HexValue)));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

Window.xaml

<Window x:Class="NumericIssue.Window"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:NumericIssue"
        xmlns:num="http://gu.se/NumericInput"
        Title="Issue" Height="100" Width="100">
    <Window.DataContext>
        <local:Viewmodel/>
    </Window.DataContext>
    
    <StackPanel>
        <num:IntBox Value="{Binding HexValue}"/>
        <num:IntBox Value="{Binding HexValue}" 
                    NumberStyles="HexNumber"/>
    </StackPanel>
</Window>

In this example, I set the initial value of a property to 0xBEEF, which is 48879 as a decimal.
While the value behind both IntBoxes is correct, the text of the second IntBox is 48879, even though it should be BEEF.
By selecting the hexadecimal text, and then the decimal text, the second box interprets the 48879 as a hexadecimal and adjusts the bound property accordingly, which results in a new value of 297081.

Demonstration: