Toolkit2/Toolkit.WinUI/TemplateControl.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Data;
using Toolkit.Foundation;

namespace Toolkit.WinUI;

[Bindable]
public class TemplateControl :
    ContentControl
{
    public TemplateControl()
    {
        DefaultStyleKey = typeof(TemplateControl);
        Loaded += OnLoaded;
    }

    private void OnLoaded(object sender,
        RoutedEventArgs args)
    {
        Loaded -= OnLoaded;

        if (DataContext is IObservableViewModel observableViewModel)
        {
            if (observableViewModel.Provider is IServiceProvider provider &&
                provider.GetRequiredKeyedService<IContentTemplateDescriptor>(DataContext.GetType().Name.Replace("ViewModel", ""))
                    is IContentTemplateDescriptor descriptor &&
                    provider.GetRequiredKeyedService(descriptor.TemplateType, descriptor.Key)
                    is FrameworkElement control)
            {
                void HandleLoaded(object? sender, RoutedEventArgs args)
                {
                    control.Loaded -= HandleLoaded;
                    if (control.DataContext is object content)
                    {
                        if (content is IActivation activation)
                        {
                            activation.IsActive = true;
                        }
                    }
                }

                void HandleDataContextChanged(FrameworkElement? sender, DataContextChangedEventArgs args)
                {
                    if (control.DataContext is object content)
                    {
                        if (content is IActivation activation)
                        {
                            activation.IsActive = true;
                        }
                    }
                }

                void HandleUnloaded(object? sender, RoutedEventArgs args)
                {
                    control.Unloaded -= HandleUnloaded;
                    if (control.DataContext is object content)
                    {
                        if (content is IActivation activation)
                        {
                            activation.IsActive = false;
                        }
                    }
                }

                control.Loaded += HandleLoaded;
                control.Unloaded += HandleUnloaded;
                control.DataContextChanged += HandleDataContextChanged;

                Content = control;
            }
        }
    }
}