Multiple bindings to a Label using XAML

I want to concatenate the FirstName and LastName. So I have implemented the FullName method that should return concatenated the FirstName and LastName but it does not happen. How to fix it ?

This is ContentView. Please, take a look to the line with "Label Text="{Binding FullName}"".

<ContentView.Content>
        <StackLayout>
            <Grid>
                <BoxView Grid.RowSpan="3" BackgroundColor="LightGreen"/>
                <Label Text="{Binding FullName}"
                       Grid.Row="0"
                       FontSize="20"
                       VerticalOptions="StartAndExpand"
                       HorizontalOptions="StartAndExpand"/>

                <Label Grid.Row="1" Text="{Binding PhoneNumber}"
                       FontSize="20"
                       VerticalOptions="StartAndExpand"
                       HorizontalOptions="StartAndExpand"/>
                <StackLayout Grid.Row="2" Orientation="Horizontal">
                    <Label Text="Select: "
                           FontSize="20"
                           VerticalOptions="Start"
                           HorizontalOptions="Start"/>
                    <CheckBox
                        VerticalOptions="Start"
                        HorizontalOptions="Start"/>
                </StackLayout>
            </Grid>
        </StackLayout>
    </ContentView.Content>

This is the code for the ContentView above

[XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class Participant : ContentView
    {
        public static readonly BindableProperty FirstNameBindableProperty =
            BindableProperty.Create(
                "FirstName",
                typeof(string),
                typeof(string),
                string.Empty);
        public static readonly BindableProperty LastNameBindableProperty =
            BindableProperty.Create(
                "LastName",
                typeof(string),
                typeof(string),
                string.Empty);
        public static readonly BindableProperty PhoneNumberBindableProperty =
            BindableProperty.Create(
                "PhoneNumber",
                typeof(string),
                typeof(string),
                string.Empty);

        public string FirstName
        {
            get { return (string)GetValue(FirstNameBindableProperty); }
            set { SetValue(FirstNameBindableProperty, value); }
        }

        public string LastName
        {
            get { return (string)GetValue(LastNameBindableProperty); }
            set { SetValue(LastNameBindableProperty, value); }
        }

        public string PhoneNumber
        {
            get { return (string)GetValue(PhoneNumberBindableProperty); }
            set { SetValue(PhoneNumberBindableProperty, value); }
        }

        public string FullName => $"{FirstName} {LastName}";

        public Participant()
        {
            InitializeComponent();
            this.BindingContext = this;
        }
    }

How to concatenate the FirstName and LastName ?