<Window 

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

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

    x:Class="Window1"

    Title="Window1" Height="346" Width="469" Name="Window1">

    <DockPanel >

        <DockPanel.Background>

            <SolidColorBrush Color="Black" />

        </DockPanel.Background>

        <WrapPanel DockPanel.Dock="Top">

            <TextBox Name="txtSource" Width="200" />    

            <Button Name="btnSelect" Width="50" Content="..." />

        </WrapPanel>

        <Rectangle DockPanel.Dock="Top" Fill="White" Height="2" />

        <StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" Name="spSmallImg"></StackPanel>

        <Rectangle DockPanel.Dock="Bottom" Fill="White" Height="2" />

        <Image  DockPanel.Dock="Bottom" Name="LargerImg"  Margin="2,2,2,2"/>

    </DockPanel>

</Window>

Imports System.Windows

Imports System.IO

Imports System.Reflection

Class Window1

    Dim smallImg() As Image

    Private Sub Window1_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded

        RefreshImage()

    End Sub

    Private Sub wpSmallImg_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles spSmallImg.MouseDown

        If e.OriginalSource.GetType.Name = "Image" Then

            LargerImg.Source = CType(e.OriginalSource, Image).Source

        End If

    End Sub

    Private Sub btnSelect_Click(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles btnSelect.Click

        Dim dlgOpen As New Windows.Forms.FolderBrowserDialog

        If dlgOpen.ShowDialog = Forms.DialogResult.OK Then

            txtSource.Text = dlgOpen.SelectedPath

            RefreshImage()

        End If

    End Sub

    Private Sub RefreshImage()

        Dim strArr() As String

        If txtSource.Text = "" Then

            strArr = IO.Directory.GetFiles("Images", "*.bmp")

        Else

            strArr = IO.Directory.GetFiles(txtSource.Text, "*.jpg")

        End If

        Dim tmpBmp As BitmapImage

        Dim tmpUri As Uri

        ReDim smallImg(strArr.Length - 1)

        spSmallImg.Children.RemoveRange(0, spSmallImg.Children.Count)

        For i As Integer = 0 To strArr.Length - 1

            If txtSource.Text = "" Then

                tmpUri = New Uri("pack://application:,,,/" & strArr(i))

            Else

                tmpUri = New Uri(strArr(i))

            End If

            tmpBmp = New BitmapImage

            tmpBmp.BeginInit()

            tmpBmp.UriSource = tmpUri

            tmpBmp.EndInit()

            smallImg(i) = New Image

            smallImg(i).Stretch = Stretch.Uniform

            smallImg(i).Width = 48

            smallImg(i).Height = 48

            smallImg(i).Source = tmpBmp

            spSmallImg.Children.Add(smallImg(i))

        Next

    End Sub

End Class