UWP - ComboBox default selected item

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" 
        Orientation="Horizontal"
        Background="GhostWhite"
        Padding="100"
        >
        <ComboBox 
            x:Name="ComboBox1" 
            Header="Select A Color"
            >
        </ComboBox>
    </StackPanel>
</Page>
MainPage.xaml.cs

using Windows.UI.Xaml.Controls;
using System.Collections.Generic;


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

            // Initialize a new list of colors
            List<string> colors = new List<string>();

            // Put some colors to the list
            colors.Add("ALICEBLUE");
            colors.Add("SEASHELL");
            colors.Add("FLORALWHITE");
            colors.Add("FORESTGREEN");
            colors.Add("MEDIUMSEAGREEN");
            colors.Add("LAWNGREEN");
            colors.Add("PAPAYAWHIP");
            colors.Add("LEMONCHIFFON");

            // Finally, Specify the ComboBox items source
            ComboBox1.ItemsSource = colors;

            /*
                SelectedIndex
                    Gets or sets the index of the selected item.
                    (Inherited from Selector)
            */

            // Set the default selected item of ComboBox
            ComboBox1.SelectedIndex = 2;

            // Alternate way to specify a default selected item 
            //ComboBox1.SelectedItem = "LAWNGREEN";
        }
    }
}