Preview 3: Complete control implementation with XAML data binding

Major milestone adding full control functionality:

Controls Enhanced:
- Entry/Editor: Full keyboard input, cursor navigation, selection, clipboard
- CollectionView: Data binding, selection highlighting, scrolling
- CheckBox/Switch/Slider: Interactive state management
- Picker/DatePicker/TimePicker: Dropdown selection with popup overlays
- ProgressBar/ActivityIndicator: Animated progress display
- Button: Press/release visual states
- Border/Frame: Rounded corners, stroke styling
- Label: Text wrapping, alignment, decorations
- Grid/StackLayout: Margin and padding support

Features Added:
- DisplayAlert dialogs with button actions
- NavigationPage with toolbar and back navigation
- Shell with flyout menu navigation
- XAML value converters for data binding
- Margin support in all layout containers
- Popup overlay system for pickers

New Samples:
- TodoApp: Full CRUD task manager with NavigationPage
- ShellDemo: Comprehensive control showcase

Removed:
- ControlGallery (replaced by ShellDemo)
- LinuxDemo (replaced by TodoApp)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

samples/TodoApp/TodoListPage.xaml.cs

@@ -0,0 +1,174 @@
+// TodoListPage - Main page for viewing todos with XAML support
+
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Graphics;
+using System.Globalization;
+
+namespace TodoApp;
+
+public partial class TodoListPage : ContentPage
+{
+    private readonly TodoService _service = TodoService.Instance;
+
+    public TodoListPage()
+    {
+        Console.WriteLine("[TodoListPage] Constructor starting");
+        InitializeComponent();
+
+        TodoCollectionView.ItemsSource = _service.Todos;
+        UpdateStats();
+
+        Console.WriteLine("[TodoListPage] Constructor finished");
+    }
+
+    protected override void OnAppearing()
+    {
+        Console.WriteLine("[TodoListPage] OnAppearing called - refreshing CollectionView");
+        base.OnAppearing();
+
+        // Refresh indexes for alternating row colors
+        _service.RefreshIndexes();
+
+        // Refresh the collection view
+        TodoCollectionView.ItemsSource = null;
+        TodoCollectionView.ItemsSource = _service.Todos;
+        Console.WriteLine($"[TodoListPage] ItemsSource set with {_service.Todos.Count} items");
+        UpdateStats();
+    }
+
+    private async void OnAddClicked(object sender, EventArgs e)
+    {
+        await Navigation.PushAsync(new NewTodoPage());
+    }
+
+    private async void OnSelectionChanged(object? sender, SelectionChangedEventArgs e)
+    {
+        try
+        {
+            Console.WriteLine($"[TodoListPage] OnSelectionChanged: {e.CurrentSelection.Count} items selected");
+            if (e.CurrentSelection.FirstOrDefault() is TodoItem todo)
+            {
+                Console.WriteLine($"[TodoListPage] Navigating to TodoDetailPage for: {todo.Title}");
+                TodoCollectionView.SelectedItem = null; // Deselect
+                var detailPage = new TodoDetailPage(todo);
+                Console.WriteLine($"[TodoListPage] Created TodoDetailPage, pushing...");
+                await Navigation.PushAsync(detailPage);
+                Console.WriteLine($"[TodoListPage] Navigation complete");
+            }
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"[TodoListPage] EXCEPTION in OnSelectionChanged: {ex.GetType().Name}: {ex.Message}");
+            Console.WriteLine($"[TodoListPage] Stack trace: {ex.StackTrace}");
+        }
+    }
+
+    private void UpdateStats()
+    {
+        var completed = _service.CompletedCount;
+        var total = _service.TotalCount;
+
+        if (total == 0)
+        {
+            StatsLabel.Text = "";
+        }
+        else
+        {
+            StatsLabel.Text = $"{completed} of {total} completed";
+        }
+    }
+}
+
+/// <summary>
+/// Converter for alternating row background colors.
+/// </summary>
+public class AlternatingRowColorConverter : IValueConverter
+{
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (value is int index)
+        {
+            return index % 2 == 0 ? Colors.White : Color.FromArgb("#F5F5F5");
+        }
+        return Colors.White;
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}
+
+/// <summary>
+/// Converter for completed task text color and indicator color.
+/// </summary>
+public class CompletedToColorConverter : IValueConverter
+{
+    // Define colors
+    private static readonly Color PrimaryColor = Color.FromArgb("#5C6BC0");
+    private static readonly Color AccentColor = Color.FromArgb("#26A69A");
+    private static readonly Color CompletedColor = Color.FromArgb("#9E9E9E");
+    private static readonly Color TextPrimary = Color.FromArgb("#212121");
+    private static readonly Color TextSecondary = Color.FromArgb("#757575");
+
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        bool isCompleted = value is bool b && b;
+        string param = parameter as string ?? "";
+
+        // Indicator bar color
+        if (param == "indicator")
+        {
+            return isCompleted ? CompletedColor : AccentColor;
+        }
+
+        // Text colors
+        if (isCompleted)
+        {
+            return CompletedColor;
+        }
+        else
+        {
+            return param == "notes" ? TextSecondary : TextPrimary;
+        }
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}
+
+/// <summary>
+/// Converter for completed task text decorations (strikethrough).
+/// </summary>
+public class CompletedToTextDecorationsConverter : IValueConverter
+{
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        bool isCompleted = value is bool b && b;
+        return isCompleted ? TextDecorations.Strikethrough : TextDecorations.None;
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}
+
+/// <summary>
+/// Converter for completed task opacity (slightly faded when complete).
+/// </summary>
+public class CompletedToOpacityConverter : IValueConverter
+{
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        bool isCompleted = value is bool b && b;
+        return isCompleted ? 0.7 : 1.0;
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}