UWP: Selectionbox Usercontrol

<UserControl

    x:Class="Rename_Images_Videos_Folder.UserControls.UcSelectionbox"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:local="using:Rename_Images_Videos_Folder.UserControls"

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    mc:Ignorable="d"

    d:DesignHeight="40"

    d:DesignWidth="400">

    <Grid>

        <TextBox  x:Name="ctlTextbox" Grid.Column="1"   Margin="0,0,29,0" 

                  VerticalAlignment="Stretch"   VerticalContentAlignment="Center" HorizontalAlignment="Stretch" 

                  KeyDown="ctlTextbox_KeyDown"

                  >

        </TextBox>

        <ComboBox Name="ctlDropDown" HorizontalAlignment="Right"  VerticalAlignment="Stretch" Width="30" MinWidth="30"

                DropDownClosed="ctlDropDown_DropDownClosed">

        </ComboBox>

    </Grid>

</UserControl>

using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Runtime.InteropServices.WindowsRuntime;

using Windows.Foundation;

using Windows.Foundation.Collections;

using Windows.UI.Xaml;

using Windows.UI.Xaml.Controls;

using Windows.UI.Xaml.Controls.Primitives;

using Windows.UI.Xaml.Data;

using Windows.UI.Xaml.Input;

using Windows.UI.Xaml.Media;

using Windows.UI.Xaml.Navigation;

namespace Rename_Images_Videos_Folder.UserControls

{

    public sealed partial class UcSelectionbox : UserControl

    {

        #region Usercontrol

        //---------------------< region: Usercontrol >----------------------

        public UcSelectionbox()

        {

            this.InitializeComponent();

        }

        //---------------------</ region: Usercontrol >----------------------

        #endregion /Usercontrol

        #region Properties

        //---------------------< region: Properties >----------------------

        public String Text {

            get { return  ctlTextbox.Text; }

            set { ctlTextbox.Text =value ; }

        }

        public String SelectedText

        {

            get { return ctlDropDown.SelectedItem.ToString(); }

            set { ctlDropDown.SelectedValue= value; }

        }

        //---------------------</ region: Properties >----------------------

        #endregion /Properties

        #region Controls

        //---------------------< region: Controls >----------------------

        private void ctlDropDown_DropDownClosed(object sender, object e)

        {

            String selectedText = ctlDropDown.SelectedItem as String;

            if (selectedText == null) return;

            ctlTextbox.Text = selectedText;

            DataContext = selectedText;

        }

        private void ctlTextbox_KeyDown(object sender, KeyRoutedEventArgs e)

        {

            if (e.Key == Windows.System.VirtualKey.Enter)

            {

                DataContext = ctlTextbox.Text;

            }

        }

        //---------------------</ region: Controls >----------------------

        #endregion /Controls

        #region Public Methods

        //---------------------< region: Public Methods >----------------------

        public void fill_Seletionbox_by_List(List<String> list_Selections)

        {

            //--< Load Selectionbox >--

            ctlDropDown.Items.Clear();

            list_Selections.Sort();

            for (int i = 0; i < list_Selections.Count; i++)

            {

                String sText = list_Selections[i];

                add_Text_To_Selection(sText);

            }

            //--</ Load Selectionbox >--

        }

        public void add_Text_To_Selection(String sText)

        {

            ctlDropDown.Items.Add(sText);

        }

        //---------------------</ region: Public Methods >----------------------

        #endregion /Public Methods

    }

}