WinUI3 ImageEx Control

using System;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Media.Imaging;

namespace PhotoOrganizer;

public class ImageEx : Control
{
    private Image? _mainImage;
    private Image? _placeholderImage;

    public string PlaceholderSource
    {
        get => (string)GetValue(PlaceholderSourceProperty);
        set => SetValue(PlaceholderSourceProperty, value);
    }

    public ImageSource Source
    {
        get => (ImageSource)GetValue(SourceProperty);
        set => SetValue(SourceProperty, value);
    }

    public static readonly DependencyProperty SourceProperty =
        DependencyProperty.Register(
            nameof(Source),
            typeof(ImageSource),
            typeof(ImageEx),
            new PropertyMetadata(null, OnSourceChanged));

    public static readonly DependencyProperty PlaceholderSourceProperty =
        DependencyProperty.Register(nameof(PlaceholderSource), typeof(string), typeof(ImageEx), new PropertyMetadata(null));

    public ImageEx() => DefaultStyleKey = typeof(ImageEx);

    protected override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        _mainImage = GetTemplateChild("MainImage") as Image;
        _placeholderImage = GetTemplateChild("PlaceholderImage") as Image;

        if (Source is BitmapImage bitmapImage)
            SetImage(bitmapImage);
        else
            ShowPlaceholder();
    }

    private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ImageEx control = (ImageEx)d;

        switch (e.NewValue)
        {
            case BitmapImage bitmapImage:
                control.SetImage(bitmapImage);
                break;
            case string uriString when !string.IsNullOrEmpty(uriString):
                control.UpdateImage(uriString);
                break;
            default:
                control.ShowPlaceholder();
                break;
        }
    }

    private void SetImage(BitmapImage image)
    {
        if (_mainImage == null)
            return;

        _mainImage.Source = image;
        _mainImage.Visibility = Visibility.Visible;

        if (_placeholderImage != null)
            _placeholderImage.Visibility = Visibility.Collapsed;
    }


    private void UpdateImage(string source)
    {
        if (string.IsNullOrEmpty(source) || !Uri.IsWellFormedUriString(source, UriKind.RelativeOrAbsolute))
            ShowPlaceholder();
        else
            ShowMainImage(source);
    }

    private void ShowPlaceholder()
    {
        if (_placeholderImage != null)
        {
            _placeholderImage.Visibility = Visibility.Visible;

            Uri placeholderUri = PlaceholderSource.StartsWith("ms-appx://")
                ? new Uri(PlaceholderSource)
                : new Uri($"ms-appx:///{PlaceholderSource}");

            _placeholderImage.Source = new BitmapImage(placeholderUri);
        }

        if (_mainImage != null)
            _mainImage.Visibility = Visibility.Collapsed;
    }

    private void ShowMainImage(string source)
    {
        if (_mainImage == null)
            return;

        try
        {
            Uri imageUri = source.StartsWith("ms-appx://")
                ? new Uri(source)
                : new Uri($"ms-appx:///{source}");

            _mainImage.Source = new BitmapImage(imageUri);
            _mainImage.Visibility = Visibility.Visible;

            if (_placeholderImage != null)
                _placeholderImage.Visibility = Visibility.Collapsed;
        }
        catch
        {
            ShowPlaceholder();
        }
    }
}