UWP - Select TextBox all text when get focus

MainPage.xaml

<Page
    x:Class="UniversalAppTutorials.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:UniversalAppTutorials"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    >
    <StackPanel Padding="50" Background="AliceBlue">
        <!--
            GotFocus
                Occurs when a UIElement receives focus.
                (Inherited from UIElement)
        -->
        <TextBox
            x:Name="TextBox1"
            PlaceholderText="Input some text here."
            Margin="5"
            GotFocus="TextBox_GotFocus"
            />
        <TextBox
            x:Name="TextBox2"
            PlaceholderText="Input some text here."
            Margin="5"
            GotFocus="TextBox_GotFocus"
            />
    </StackPanel>
</Page>
MainPage.xaml.cs

using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml;


namespace UniversalAppTutorials
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        void TextBox_GotFocus(object sender, RoutedEventArgs e)
        {
            // Get the instance of TextBox
            TextBox textBox = sender as TextBox;

            // Select all existing text of TextBox on focus
            textBox.SelectAll();
        }
    }
}