Introducing Apex

<Window x:Class="MVVMSample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:MVVMSample"
        Title="MainWindow" Height="200" Width="300">
    
    <!-- The datacontext for the window is an instance of our viewmodel. -->
    <Window.DataContext>
        <local:MainViewModel x:Name="viewModel" />
    </Window.DataContext>
    
    <Grid>
        <StackPanel>
            <TextBlock Text="First Name" />
            <TextBox Margin="4" Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}" />
            <TextBlock Text="Second Name" />
            <TextBox Margin="4" Text="{Binding SecondName, UpdateSourceTrigger=PropertyChanged}" />
            <Button Margin="4" Width="80" Content="Build Name" Command="{Binding BuildNameCommand}" />
            <TextBox Margin="4" Text="{Binding FullName}" />
        </StackPanel>
    </Grid>
</Window>