UWP - How to use RadioButton

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 
        x:Name="stack_panel1" 
        Margin="50" 
        Orientation="Vertical"
        Background="AliceBlue"
        Padding="35"
        >
        <TextBlock 
            x:Name="text_block1"
            TextWrapping="WrapWholeWords"
            Text="Change This text color by choosing a color from radio btton group."
            Margin="0,0,0,10"
            FontSize="30"
            FontFamily="s"
            />
        <TextBlock
            Text="Choose a Color."
            Margin="10"
            FontWeight="Black"
            />
        <StackPanel 
            Orientation="Horizontal" 
            Background="Orange"
            Padding="20"
            >
            <RadioButton 
                Content="Red" 
                Tag="Red" 
                Checked="Color_RadioButton_Checked" 
                GroupName="TextColor"
                />
            <RadioButton 
                Content="Green" 
                Tag="Green" 
                Checked="Color_RadioButton_Checked"  
                GroupName="TextColor"
                />
            <RadioButton 
                Content="Blue" 
                Tag="Blue" 
                Checked="Color_RadioButton_Checked" 
                GroupName="TextColor"
                />
            <RadioButton 
                Content="Yellow" 
                Tag="Yellow" 
                Checked="Color_RadioButton_Checked" 
                GroupName="TextColor"
                />
        </StackPanel>
    </StackPanel>
</Page>
MainPage.xaml.cs

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


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

        private void Color_RadioButton_Checked(object sender, RoutedEventArgs e) {
            // Get the instance of clicked RadioButton instance
            RadioButton rb = (RadioButton)sender;

            if (rb != null && text_block1 != null) {

                string selectedColor = rb.Tag.ToString();

                switch (selectedColor) {
                    case "Red":
                        text_block1.Foreground = new SolidColorBrush(Colors.Red);
                        break;
                    case "Green":
                        text_block1.Foreground = new SolidColorBrush(Colors.Green);
                        break;
                    case "Blue":
                        text_block1.Foreground = new SolidColorBrush(Colors.Blue);
                        break;
                    case "Yellow":
                        text_block1.Foreground = new SolidColorBrush(Colors.Yellow);
                        break;
                }
            }
        }
    }
}