WPF

<Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Border Width="385" Height="385" Margin="0,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" CornerRadius="8" Background="#FF0085C8">
</Grid>

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
</Window>

Class MainWindow
    Private Sub MainWindow_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
        Dim GridUri As New Uri("Resources\theme.xaml", UriKind.Relative)
        Dim sri As Windows.Resources.StreamResourceInfo = Application.GetResourceStream(GridUri)
        Dim xrdr As New System.Windows.Markup.XamlReader()
        Dim grd As Grid = CType(xrdr.LoadAsync(sri.Stream), Grid)
        Me.Content = grd
    End Sub
End Class

System.Windows.Controls.AutoCompleteBox

<Window x:Class="auotocomplitetrial.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:toolkit="clr-  namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <toolkit:AutoCompleteBox Name="autocompleteBox"  Height="50" Width="300"
                                 ItemsSource="{Binding MyList}"
                                 IsTextCompletionEnabled="True">
        </toolkit:AutoCompleteBox>
    </Grid>
</Window>

public partial class MainWindow : Window
 {
     private List<string> myList;

     public List<string> MyList
     {
         get { return myList; }
     }

     public MainWindow()
     {
         InitializeComponent();

         myList = new List<string>
                          {
                              "Macedonia",
                              "Madagascar",
                              "Malawi",
                              "Malaysia",
                              "Maldives",
                              "Mali",
                              "Malta",
                              "Marshall Islands",
                              "Mauritania",
                              "Mauritius",
                              "Mexico",
                              "Micronesia",
                              "Moldova",
                              "Monaco",
                              "Mongolia",
                              "Montenegro",
                              "Morocco",
                              "Mozambique",
                              "Myanmar"
                          };
         //autocompleteBox.ItemsSource = myList;
     }
 }

//autocompleteBox.ItemsSource = myList;

ItemsSource="{Binding MyList}"