MainWindow.xaml

<Window x:Class="LetterClassifier.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:LetterClassifier"
        mc:Ignorable="d"
        Title="Letter Classifier" Height="450" Width="800">
    <Window.DataContext>
        <local:MainViewModel />
    </Window.DataContext>
    <Window.Resources>
        <local:PathToImageSourceConverter x:Key="PathToImageSourceConverter" />
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <Menu>
            <MenuItem Header="File">
                <MenuItem Header="Load Classifications" Command="{Binding Path=LoadClassificationsCommand}" />
                <MenuItem Header="Save Classifications" Command="{Binding Path=SaveClassificationsCommand}" />
            </MenuItem>
        </Menu>
        <Image Grid.Row="1" Source="{Binding Path=ImagePath.Value, Converter={StaticResource PathToImageSourceConverter}}" />
        <TextBox Grid.Row="2" Text="{Binding Path=Letter.Value, UpdateSourceTrigger=PropertyChanged}" FontSize="18" HorizontalContentAlignment="Center" />
        <Button Grid.Row="3" Command="{Binding Path=LabelImageCommand}" IsDefault="True" FontSize="18">Label</Button>
    </Grid>
</Window>