MainPage.xaml

<Page
    x:Class="FileMerger.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:FileMerger"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Grid>
        <Button Content="Select Clips" Click="Select_OnClick" Height="76" Margin="180,156,0,0" VerticalAlignment="Top" Width="374"/>
        <Button Content="Merge" Click="Merge_OnClick" Height="86" Margin="180,308,0,0" VerticalAlignment="Top" Width="374"/>
        <TextBlock Name="TextBlock" HorizontalAlignment="Left" Height="138" Margin="721,194,0,0" Text="" TextWrapping="Wrap" VerticalAlignment="Top" Width="388"/>
    </Grid>
</Page>