No FrameHandler in WinUI for now... its too complex and broken

Toolkit.Foundation/ObservableCollection.cs

@@ -181,6 +181,8 @@ public partial class ObservableCollection<TViewModel> :
 
             Add(item);
         }
+
+        SelectedItem = this.FirstOrDefault();
     }
 
     public void Clear(bool disposeItems = false)

Toolkit.UI.WinUI/WindowExtensions.cs

@@ -10,6 +10,7 @@ using Windows.Win32.UI.WindowsAndMessaging;
 using Toolkit.Windows;
 using Rect = Windows.Foundation.Rect;
 using WinUIEx;
+using Windows.Graphics;
 
 namespace Toolkit.UI.WinUI;
 
@@ -34,6 +35,17 @@ public static partial class WindowExtensions
         }
     }
 
+    public static void SetSize(this Window window,
+        int width, 
+        int height)
+    {
+        nint handle = WindowNative.GetWindowHandle(window);
+        if (handle == 0) return;
+
+        float value = PInvoke.GetDpiForWindow(new HWND(handle)) / 96f;
+        window.AppWindow.Resize(new SizeInt32((int)(width * (double)value), (int)(height * (double)value)));
+    }
+
     public static void MoveAndResize(this Window window,
         Rect rect)
     {
@@ -48,7 +60,7 @@ public static partial class WindowExtensions
     }
 
     public static void SetBorderless(this Window window,
-                bool value)
+        bool value)
     {
         WindowStyle windowStyle = window.GetWindowStyle();
 

Toolkit.WinUI/ContentTemplate.cs

@@ -29,15 +29,17 @@ public class ContentTemplate :
     }
 
     protected override DataTemplate? SelectTemplateCore(object item,
-        DependencyObject container) => SelectTemplateCore(item);
+        DependencyObject container)
+    {
+        return SelectTemplateCore(item);
+    }
 
     private static DataTemplate CreateDataTemplate(IContentTemplateDescriptor descriptor)
     {
         string xamlString = @$"
                 <DataTemplate xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation""
-                              xmlns:x=""http://schemas.microsoft.com/winfx/2006/xaml""
+                              xmlns:ui=""using:{descriptor.TemplateType.Namespace}"">
-                              xmlns:local=""using:Toolkit.WinUI"">
+                      <ui:{descriptor.TemplateType.Name} />
-                    <local:TemplateControl />
                 </DataTemplate>";
 
         return (DataTemplate)XamlReader.Load(xamlString);

Toolkit.WinUI/PageControl.cs

@@ -1,9 +0,0 @@
-using Microsoft.UI.Xaml.Controls;
-
-namespace Toolkit.WinUI;
-
-public class PageControl : 
-    Page
-{
-
-}

Toolkit.WinUI/TemplatePage.xaml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Page
+    x:Class="Toolkit.WinUI.TemplatePage"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" />

Toolkit.WinUI/TemplatePage.xaml.cs

@@ -0,0 +1,8 @@
+using Microsoft.UI.Xaml.Controls;
+
+namespace Toolkit.WinUI;
+
+public sealed partial class TemplatePage : Page
+{
+    public TemplatePage() => InitializeComponent();
+}

Toolkit.WinUI/Toolkit.WinUI.csproj

@@ -15,6 +15,10 @@
 		<UseWinUI>true</UseWinUI>
 		<WindowsSdkPackageVersion>10.0.19041.41</WindowsSdkPackageVersion>
 	</PropertyGroup>
+
+	<ItemGroup>
+	  <None Remove="TemplatePage.xaml" />
+	</ItemGroup>
 	
 	<ItemGroup>
 		<PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.26100.1742" />
@@ -24,5 +28,11 @@
 	<ItemGroup>
 		<ProjectReference Include="..\Toolkit.Windows\Toolkit.Windows.csproj" />
 	</ItemGroup>
+	
+	<ItemGroup>
+	  <Page Update="TemplatePage.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </Page>
+	</ItemGroup>
 
 </Project>