MainWindow.xaml

<Window
    x:Class="WinUI3_IFileDialog.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:WinUI3_IFileDialog"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <!--<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Button x:Name="myButton" Click="myButton_Click">Choose Files</Button>
    </StackPanel>-->
    <Grid>

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"></ColumnDefinition>
            <!--<ColumnDefinition Width="10"></ColumnDefinition>-->
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="500"></RowDefinition>
            <!--<RowDefinition Height="60"></RowDefinition>-->
            <RowDefinition Height="*"></RowDefinition>
        </Grid.RowDefinitions>
        
        <StackPanel Orientation="Horizontal" Grid.Column="0" Grid.Row="0" HorizontalAlignment="Left" VerticalAlignment="Center">
            <StackPanel Orientation="Vertical" VerticalAlignment="Center">
                <Button x:Name="btnChooseFiles" Click="btnChooseFiles_Click" Margin="5,5,5,5">Choose Files</Button>
                <Button x:Name="btnChooseDirectory" Click="btnChooseDirectory_Click" Margin="5,5,5,5">Choose Directory</Button>
                <Button x:Name="btnChooseFilesDirectories" Click="btnChooseFilesDirectories_Click" Margin="5,5,5,5"
                        Content="Choose Files &amp; Directories&#x0a;     with custom Button">                    
                </Button>
                <Button x:Name="btnSaveFile" Click="btnSaveFile_Click" Margin="5,5,5,5">Save File (virtually)</Button>
            </StackPanel>
            <ListView x:Name="lvFiles" ItemsSource="{x:Bind files}"
                Height="400" MinWidth="550" BorderThickness="1" BorderBrush="{ThemeResource SystemControlForegroundBaseMediumLowBrush}">

                <ListView.Resources>
                    <SolidColorBrush x:Key="ListViewItemBackgroundSelected" Color="Blue" />
                    <SolidColorBrush x:Key="ListViewItemBackgroundSelectedPointerOver" Color="Blue" />
                </ListView.Resources>

                <ListView.HeaderTemplate>
                    <DataTemplate>
                        <Grid Padding="12" Background="{ThemeResource SystemBaseLowColor}">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="608"/>
                                <!--<ColumnDefinition Width="360"/>-->
                                <ColumnDefinition Width="100"/>
                            </Grid.ColumnDefinitions>
                            <TextBlock Text="File name" Style="{ThemeResource CaptionTextBlockStyle}"/>
                            <!--<TextBlock Grid.Column="1" Text="File Name" Style="{ThemeResource CaptionTextBlockStyle}"/>-->
                            <TextBlock Grid.Column="2" Text="Type" Style="{ThemeResource CaptionTextBlockStyle}"/>
                        </Grid>
                    </DataTemplate>
                </ListView.HeaderTemplate>

                <ListView.ItemTemplate>
                    <DataTemplate x:Name="TableDataTemplate" x:DataType="local:File">
                        <Grid Height="48" AutomationProperties.Name="{x:Bind Name}">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="48"/>
                                <ColumnDefinition Width="560"/>
                                <ColumnDefinition Width="100"/>
                            </Grid.ColumnDefinitions>
                            <!--<Ellipse Height="32" Width="32" VerticalAlignment="Center">
                                <Ellipse.Fill>
                                    <ImageBrush ImageSource="Assets/Butterfly.png"/>
                                </Ellipse.Fill>
                            </Ellipse>-->
                            <Image Source="{x:Bind biFileThumbnail}" MaxWidth="32" MaxHeight="32" Stretch="Fill"/>
                            <TextBlock Grid.Column="1" VerticalAlignment="Center" Style="{ThemeResource BaseTextBlockStyle}" Text="{x:Bind Name}" />
                            <TextBlock Grid.Column="2" VerticalAlignment="Center" HorizontalAlignment="Left" Text="{x:Bind Type}"/>                           
                        </Grid>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </StackPanel>
    </Grid>
</Window>