Add Content lookup markupextension

Framework/Avalonia/Contents/ContentTemplateSelector.cs

@@ -0,0 +1,37 @@
+using Avalonia.Controls;
+using Avalonia.Controls.Templates;
+using Toolkit.Framework.Foundation;
+
+namespace Toolkit.Framework.Avalonia;
+
+public class ContentTemplateSelector : IDataTemplate, IContentTemplateSelector
+{
+    private readonly Dictionary<object, IControl> dataTracking = new();
+
+    private readonly IContentTemplateFactory templateFactory;
+
+    public ContentTemplateSelector(IContentTemplateFactory templateFactory)
+    {
+        this.templateFactory = templateFactory;
+    }
+
+    public IControl? Build(object? item)
+    {
+        if (item is not null)
+        {
+            if (dataTracking.TryGetValue(item, out IControl? control))
+            {
+                return control;
+            }
+
+            return (IControl?)templateFactory.Create(item);
+        }
+
+        return null;
+    }
+
+    public bool Match(object? data)
+    {
+        return true;
+    }
+}