Markup Extensions & Namescopes

<!-- Positional: calls the constructor that takes one parameter. -->
<TextBlock Text="{x:Static local:BookshelfConstants.AppTitle}" />

<!-- Named: sets the Member property after the parameterless constructor. -->
<TextBlock Text="{x:Static Member=local:BookshelfConstants.AppTitle}" />

<!-- Binding mixes both: Path is positional, the rest are named. -->
<TextBox Text="{Binding SearchText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Delay=250}" />

<Window x:Class="Bookshelf.Desktop.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:vm="clr-namespace:Bookshelf.Desktop.ViewModels"
        mc:Ignorable="d"
        d:DataContext="{d:DesignInstance Type=vm:BooksViewModel}"
        Title="Bookshelf Desktop" Width="900" Height="560">
    <!-- BooksViewModel has constructor dependencies, so the real DataContext is set in the
         code-behind constructor from dependency injection; d:DataContext only types the bindings. -->
    <DockPanel Margin="12">
        <TextBox x:Name="SearchBox" DockPanel.Dock="Top" Margin="0,0,0,8"
                 Text="{Binding SearchText, UpdateSourceTrigger=PropertyChanged, Delay=250}" />
        <ListView ItemsSource="{Binding Books}"
                  SelectedItem="{Binding SelectedBook, Mode=TwoWay}"
                  DisplayMemberPath="Title" />
    </DockPanel>
</Window>

<Window.Resources>
    <!-- Defined first: StaticResource needs it before use. -->
    <local:BooleanToVisibilityConverter x:Key="BoolToVisibility" />
    <SolidColorBrush x:Key="AccentBrush" Color="#0F6CBD" />
</Window.Resources>

<StackPanel>
    <!-- Never changes: StaticResource. -->
    <TextBlock Text="Bookshelf" Foreground="{StaticResource AccentBrush}" />

    <!-- Replaced when the theme dictionary is swapped: DynamicResource. -->
    <Border Background="{DynamicResource CardBackgroundBrush}">
        <TextBlock Text="{Binding SelectedBook.Title}" />
    </Border>

    <TextBlock Text="Loading..."
               Visibility="{Binding IsBusy, Converter={StaticResource BoolToVisibility}}" />
</StackPanel>

<Style x:Key="BookCardStyle" TargetType="{x:Type ContentControl}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ContentControl}">
                <Border Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        Padding="{TemplateBinding Padding}"
                        CornerRadius="6">
                    <ContentPresenter />
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

<!-- In a DataTemplate: reach the ListView's DataContext from each item. -->
<DataTemplate DataType="{x:Type vm:BookViewModel}">
    <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding Title}" />
        <Button Content="Remove" Margin="8,0,0,0"
                Command="{Binding DataContext.RemoveBookCommand,
                          RelativeSource={RelativeSource AncestorType={x:Type ListView}}}"
                CommandParameter="{Binding}" />
    </StackPanel>
</DataTemplate>

using System.Windows;

namespace Bookshelf.Desktop;

public static class BookshelfConstants
{
    public const string AppTitle = "Bookshelf Desktop";
    public const int MaxSearchResults = 200;
    public static readonly Thickness CardMargin = new(0, 0, 0, 8);
}

<Window xmlns:local="clr-namespace:Bookshelf.Desktop"
        Title="{x:Static local:BookshelfConstants.AppTitle}">
    <StackPanel>
        <TextBlock Margin="{x:Static local:BookshelfConstants.CardMargin}"
                   Text="{x:Static local:BookshelfConstants.AppTitle}" />
        <!-- Show an enum member without code-behind. -->
        <ComboBox SelectedItem="{x:Static HorizontalAlignment.Stretch}" />
        <!-- Remove a value inherited from a style. -->
        <Button Content="Plain" Background="{x:Null}" />
    </StackPanel>
</Window>

<StackPanel>
    <!-- Shows the literal text {Binding Title} in the help text. -->
    <TextBlock Text="{}{Binding Title} shows the book title." />
    <TextBlock Text="\{x:Static\} reads a static member." />
    <!-- A string format containing braces needs the empty pair too. -->
    <TextBlock Text="{Binding Price, StringFormat={}{0:C2}}" />
</StackPanel>

using System.Globalization;
using System.Resources;
using System.Windows.Markup;

namespace Bookshelf.Desktop.Markup;

[MarkupExtensionReturnType(typeof(string))]
public sealed class LocExtension : MarkupExtension
{
    private static readonly ResourceManager Resources =
        new("Bookshelf.Desktop.Properties.Strings", typeof(LocExtension).Assembly);

    public LocExtension() { }

    public LocExtension(string key) => Key = key;

    [ConstructorArgument("key")]
    public string? Key { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (string.IsNullOrEmpty(Key))
        {
            throw new InvalidOperationException("Loc requires a resource key.");
        }

        // Look the key up with the current UI culture: English or Spanish.
        return Resources.GetString(Key, CultureInfo.CurrentUICulture) ?? $"!{Key}!";
    }
}

<Window xmlns:mk="clr-namespace:Bookshelf.Desktop.Markup">
    <StackPanel>
        <TextBlock Text="{mk:Loc BookList_Title}" />
        <Button Content="{mk:Loc Key=Action_Add}" Command="{Binding AddBookCommand}" />
    </StackPanel>
</Window>

using System.Windows;
using System.Windows.Markup;
using System.Windows.Media;

namespace Bookshelf.Desktop.Markup;

public enum BookStatus
{
    WantToRead,
    Reading,
    Finished,
}

[MarkupExtensionReturnType(typeof(object))]
public sealed class BookStatusExtension : MarkupExtension
{
    public BookStatusExtension() { }

    public BookStatusExtension(BookStatus status) => Status = status;

    [ConstructorArgument("status")]
    public BookStatus Status { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var target = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;

        // At design time or inside a Setter the target can be a SharedDp or null; fall back to the enum.
        var propertyType = target?.TargetProperty switch
        {
            DependencyProperty dp => dp.PropertyType,
            System.Reflection.PropertyInfo pi => pi.PropertyType,
            _ => typeof(object),
        };

        if (typeof(Brush).IsAssignableFrom(propertyType))
        {
            return Status switch
            {
                BookStatus.Reading => Brushes.SteelBlue,
                BookStatus.Finished => Brushes.SeaGreen,
                _ => Brushes.Gray,
            };
        }

        if (propertyType == typeof(string))
        {
            return Status.ToString();
        }

        return Status;
    }
}

<Border xmlns:mk="clr-namespace:Bookshelf.Desktop.Markup"
        Background="{mk:BookStatus Reading}" Padding="6">
    <TextBlock Text="{mk:BookStatus Status=Reading}" />
</Border>

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Animation;

namespace Bookshelf.Desktop;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        Loaded += (_, _) => PulseSearchBox();
    }

    private void PulseSearchBox()
    {
        // SearchBox is registered by InitializeComponent in the Window namescope.
        var box = (TextBox)FindName("SearchBox");

        // A storyboard built in code needs the target to be registered by name.
        var brush = new SolidColorBrush(Colors.Transparent);
        box.Background = brush;
        RegisterName("SearchBrush", brush);

        var animation = new ColorAnimation(Colors.LightYellow, TimeSpan.FromMilliseconds(400))
        {
            AutoReverse = true,
        };
        Storyboard.SetTargetName(animation, "SearchBrush");
        Storyboard.SetTargetProperty(animation, new PropertyPath(SolidColorBrush.ColorProperty));

        var storyboard = new Storyboard();
        storyboard.Children.Add(animation);
        storyboard.Begin(this);
    }

    private void OnBookSelected(object sender, SelectionChangedEventArgs e)
    {
        // Reach a named element inside a ListView item's template.
        if (BooksList.ItemContainerGenerator.ContainerFromItem(BooksList.SelectedItem)
            is ListViewItem item)
        {
            var presenter = FindVisualChild<ContentPresenter>(item);
            var title = (TextBlock?)presenter?.ContentTemplate.FindName("TitleText", presenter);
            title?.Focus();
        }
    }

    private static T? FindVisualChild<T>(DependencyObject parent)
        where T : DependencyObject
    {
        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
        {
            var child = VisualTreeHelper.GetChild(parent, i);
            if (child is T match)
            {
                return match;
            }

            if (FindVisualChild<T>(child) is { } nested)
            {
                return nested;
            }
        }

        return default;
    }
}

<ControlTemplate x:Key="BookCardTemplate" TargetType="{x:Type ContentControl}">
    <Border x:Name="PART_Card" Background="{DynamicResource CardBackgroundBrush}" Padding="8">
        <StackPanel>
            <Image x:Name="PART_Cover" Width="64" Height="96" />
            <ContentPresenter />
        </StackPanel>
    </Border>
    <ControlTemplate.Triggers>
        <Trigger Property="IsMouseOver" Value="True">
            <Setter TargetName="PART_Card" Property="Background"
                    Value="{DynamicResource CardHoverBackgroundBrush}" />
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>