Add project files.

Framework/Avalonia/Templates/TemplateSelector.cs

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+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Markup.Xaml.Templates;
+using FluentAvalonia.UI.Controls;
+using TheXamlGuy.Framework.Core;
+
+namespace TheXamlGuy.Framework.Avalonia;
+
+public class TemplateSelector : DataTemplateSelector, ITemplateSelector
+{
+    private readonly Dictionary<object, DataTemplate> dataTracking = new();
+
+    private readonly ITemplateFactory templateFactory;
+    private readonly IEventAggregator eventAggregator;
+
+    public TemplateSelector(ITemplateFactory templateFactory, 
+        IEventAggregator eventAggregator)
+    {
+        this.templateFactory = templateFactory;
+        this.eventAggregator = eventAggregator;
+    }
+
+    protected override IDataTemplate SelectTemplateCore(object item, IControl container)
+    {
+        if (item is not null)
+        {
+            if (dataTracking.TryGetValue(item, out DataTemplate? cachedDataTemplate))
+            {
+                return cachedDataTemplate;
+            }
+
+            return new FuncDataTemplate(item.GetType(), (value, namescope) =>
+            {
+                if (templateFactory.Create(item) is TemplatedControl template)
+                {
+                    return template;
+                }
+
+                return null;
+            });
+                        
+        }
+
+        return base.SelectTemplateCore(item, container);
+    }
+}