ObservableFieldItemDictionarySelector.cs

using System;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Reflection;
using Microsoft.Maui.Controls;
using NeuroAccessMaui.UI.Pages.Identity.ObjectModel;
 
 
namespace NeuroAccessMaui.UI.Pages.Identity.ViewIdentity
{
    public class TemplateMapping
    {
        public required string Key { get; set; }
 
        public required DataTemplate Template { get; set; }
    }
    public class ObservableFieldItemDictionarySelector : DataTemplateSelector
    {
        // 1) Use ObservableCollection so we can hook CollectionChanged
        public ObservableCollection<TemplateMapping> Templates { get; }
            = [];
 
        public DataTemplate? DefaultTemplate { get; set; }
 
        // backing template map
        private Dictionary<string, DataTemplate>? templateMap;
 
        public ObservableFieldItemDictionarySelector()
        {
            this.Templates.CollectionChanged += this.OnTemplatesChanged;
        }
 
        void OnTemplatesChanged(object? sender, NotifyCollectionChangedEventArgs e)
        {
            this.templateMap = null;
        }
 
        protected override DataTemplate? OnSelectTemplate(object item, BindableObject container)
        {
            // populate template map
            this.templateMap ??= this.Templates
                      .Where(m => !string.IsNullOrEmpty(m.Key) && m.Template is not null)
                      .ToDictionary(m => m.Key!, m => m.Template!);
 
            if (item is ObservableFieldItem Field
                && !string.IsNullOrEmpty(Field.Key)
                && this.templateMap.TryGetValue(Field.Key, out DataTemplate? Template))
            {
                return Template;
            }
 
            return this.DefaultTemplate;
        }
    }
}