known working commit:

This is the SDK of 73786cd, but with changes:
*  the `IExtendedAttributesProvider` commented off of the `CommandItem`
* and we move IEAP onto ListItem. It's implemented by the base
  CommandItem's GetProperties. This does work.

so at least we have _something_ to work with.

src/modules/cmdpal/ext/SamplePagesExtension/Program.cs

@@ -1,10 +1,12 @@
-// Copyright (c) Microsoft Corporation
+// Copyright (c) Microsoft Corporation
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
 using System;
 using System.Threading;
 using Microsoft.CommandPalette.Extensions;
+using Shmuelie.WinRTServer;
+using Shmuelie.WinRTServer.CsWinRT;
 
 namespace SamplePagesExtension;
 
@@ -15,18 +17,22 @@ public class Program
     {
         if (args.Length > 0 && args[0] == "-RegisterProcessAsComServer")
         {
-            using ExtensionServer server = new();
-            var extensionDisposedEvent = new ManualResetEvent(false);
-            var extensionInstance = new SampleExtension(extensionDisposedEvent);
+            global::Shmuelie.WinRTServer.ComServer server = new();
+
+            ManualResetEvent extensionDisposedEvent = new(false);
 
             // We are instantiating an extension instance once above, and returning it every time the callback in RegisterExtension below is called.
             // This makes sure that only one instance of SampleExtension is alive, which is returned every time the host asks for the IExtension object.
             // If you want to instantiate a new instance each time the host asks, create the new instance inside the delegate.
-            server.RegisterExtension(() => extensionInstance);
+            SampleExtension extensionInstance = new(extensionDisposedEvent);
+            server.RegisterClass<SampleExtension, IExtension>(() => extensionInstance);
+            server.Start();
 
             // This will make the main thread wait until the event is signalled by the extension class.
-            // Since we have a single instance of the extension object, we exit as soon as it is disposed.
+            // Since we have single instance of the extension object, we exit as soon as it is disposed.
             extensionDisposedEvent.WaitOne();
+            server.Stop();
+            server.UnsafeDispose();
         }
         else
         {

src/modules/cmdpal/ext/SamplePagesExtension/SamplePagesExtension.csproj

@@ -34,6 +34,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="Shmuelie.WinRTServer" />
     <PackageReference Include="Microsoft.WindowsAppSDK" />
     <PackageReference Include="Microsoft.Windows.CsWin32">
       <PrivateAssets>all</PrivateAssets>

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/BaseObservable.cs

@@ -2,7 +2,6 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Runtime.CompilerServices;
 using Windows.Foundation;
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
@@ -15,7 +14,7 @@ public partial class BaseObservable : INotifyPropChanged
 {
     public event TypedEventHandler<object, IPropChangedEventArgs>? PropChanged;
 
-    protected void OnPropertyChanged([CallerMemberName] string? propertyName = null)
+    protected void OnPropertyChanged(string propertyName)
     {
         try
         {
@@ -23,37 +22,10 @@ public partial class BaseObservable : INotifyPropChanged
             // this can crash as we try to invoke the handlers from that process.
             // However, just catching it seems to still raise the event on the
             // new host?
-            PropChanged?.Invoke(this, new PropChangedEventArgs(propertyName!));
+            PropChanged?.Invoke(this, new PropChangedEventArgs(propertyName));
         }
         catch
         {
         }
     }
-
-    /// <summary>
-    /// Sets the backing field to the specified value and raises a property changed
-    /// notification if the value is different from the current one.
-    /// </summary>
-    /// <typeparam name="T">The type of the property.</typeparam>
-    /// <param name="field">A reference to the backing field for the property.</param>
-    /// <param name="value">The new value to assign to the property.</param>
-    /// <param name="propertyName">
-    /// The name of the property. This is optional and is usually supplied
-    /// automatically by the <see cref="CallerMemberNameAttribute"/>.
-    /// </param>
-    /// <returns>
-    /// <see langword="true"/> if the field was updated and a property changed
-    /// notification was raised; otherwise, <see langword="false"/>.
-    /// </returns>
-    protected bool SetProperty<T>(ref T field, T value, [CallerMemberName] string? propertyName = null)
-    {
-        if (EqualityComparer<T>.Default.Equals(field, value))
-        {
-            return false;
-        }
-
-        field = value;
-        OnPropertyChanged(propertyName!);
-        return true;
-    }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Command.cs

@@ -6,11 +6,31 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class Command : BaseObservable, ICommand
 {
-    public virtual string Name { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Name
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Name));
+        }
+    }
+
+= string.Empty;
 
     public virtual string Id { get; set; } = string.Empty;
 
-    public virtual IconInfo Icon { get; set => SetProperty(ref field, value); } = new();
+    public virtual IconInfo Icon
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Icon));
+        }
+    }
+
+= new();
 
     IIconInfo ICommand.Icon => Icon;
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/CommandContextItem.cs

@@ -6,9 +6,9 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class CommandContextItem : CommandItem, ICommandContextItem
 {
-    public virtual bool IsCritical { get; set => SetProperty(ref field, value); }
+    public virtual bool IsCritical { get; set; }
 
-    public virtual KeyChord RequestedShortcut { get; set => SetProperty(ref field, value); }
+    public virtual KeyChord RequestedShortcut { get; set; }
 
     public CommandContextItem(ICommand command)
         : base(command)

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/CommandItem.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation
+// Copyright (c) Microsoft Corporation
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
@@ -8,7 +8,7 @@ using WinRT;
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
-public partial class CommandItem : BaseObservable, ICommandItem, IExtendedAttributesProvider
+public partial class CommandItem : BaseObservable, ICommandItem
 {
     private readonly PropertySet _extendedAttributes = new();
 
@@ -19,36 +19,44 @@ public partial class CommandItem : BaseObservable, ICommandItem, IExtendedAttrib
     private DataPackage? _dataPackage;
     private DataPackageView? _dataPackageView;
 
-    public virtual IIconInfo? Icon { get; set => SetProperty(ref field, value); }
+    public virtual IIconInfo? Icon
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Icon));
+        }
+    }
 
     public virtual string Title
     {
         get => !string.IsNullOrEmpty(_title) ? _title : _command?.Name ?? string.Empty;
+
         set
         {
-            var oldTitle = Title;
             _title = value;
-            if (Title != oldTitle)
-            {
-                OnPropertyChanged();
-            }
+            OnPropertyChanged(nameof(Title));
         }
     }
 
-    public virtual string Subtitle { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Subtitle
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Subtitle));
+        }
+    }
+
+= string.Empty;
 
     public virtual ICommand? Command
     {
         get => _command;
         set
         {
-            if (EqualityComparer<ICommand?>.Default.Equals(value, _command))
-            {
-                return;
-            }
-
-            var oldTitle = Title;
-
             if (_commandListener is not null)
             {
                 _commandListener.Detach();
@@ -63,8 +71,8 @@ public partial class CommandItem : BaseObservable, ICommandItem, IExtendedAttrib
                 value.PropChanged += _commandListener.OnEvent;
             }
 
-            OnPropertyChanged();
-            if (string.IsNullOrEmpty(_title) && oldTitle != Title)
+            OnPropertyChanged(nameof(Command));
+            if (string.IsNullOrEmpty(_title))
             {
                 OnPropertyChanged(nameof(Title));
             }
@@ -80,7 +88,17 @@ public partial class CommandItem : BaseObservable, ICommandItem, IExtendedAttrib
         }
     }
 
-    public virtual IContextItem[] MoreCommands { get; set => SetProperty(ref field, value); } = [];
+    public virtual IContextItem[] MoreCommands
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(MoreCommands));
+        }
+    }
+
+= [];
 
     public DataPackage? DataPackage
     {

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/CommandResult.cs

@@ -6,9 +6,9 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class CommandResult : ICommandResult
 {
-    public ICommandResultArgs? Args { get; private init; }
+    public ICommandResultArgs? Args { get; private set; }
 
-    public CommandResultKind Kind { get; private init; } = CommandResultKind.Dismiss;
+    public CommandResultKind Kind { get; private set; } = CommandResultKind.Dismiss;
 
     public static CommandResult Dismiss()
     {

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/ContentPage.cs

@@ -10,9 +10,17 @@ public abstract partial class ContentPage : Page, IContentPage
 {
     public event TypedEventHandler<object, IItemsChangedEventArgs>? ItemsChanged;
 
-    public virtual IDetails? Details { get; set => SetProperty(ref field, value); }
+    public virtual IDetails? Details
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Details));
+        }
+    }
 
-    public virtual IContextItem[] Commands { get; set => SetProperty(ref field, value); } = [];
+    public virtual IContextItem[] Commands { get; set; } = [];
 
     public abstract IContent[] GetContent();
 

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Details.cs

@@ -7,15 +7,65 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class Details : BaseObservable, IDetails, IExtendedAttributesProvider
 {
-    public virtual IIconInfo HeroImage { get; set => SetProperty(ref field, value); } = new IconInfo();
+    public virtual IIconInfo HeroImage
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(HeroImage));
+        }
+    }
 
-    public virtual string Title { get; set => SetProperty(ref field, value); } = string.Empty;
+= new IconInfo();
 
-    public virtual string Body { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Title
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Title));
+        }
+    }
 
-    public virtual IDetailsElement[] Metadata { get; set => SetProperty(ref field, value); } = [];
+= string.Empty;
 
-    public virtual ContentSize Size { get; set => SetProperty(ref field, value); } = ContentSize.Small;
+    public virtual string Body
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Body));
+        }
+    }
+
+= string.Empty;
+
+    public virtual IDetailsElement[] Metadata
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Metadata));
+        }
+    }
+
+= [];
+
+    public virtual ContentSize Size
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Size));
+        }
+    }
+
+= ContentSize.Small;
 
     public IDictionary<string, object>? GetProperties() => new ValueSet()
     {

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Dock/WrappedDockItem.cs

@@ -0,0 +1,124 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CommandPalette.Extensions.Toolkit;
+
+#pragma warning disable SA1402 // File may only contain a single type
+
+public partial class WrappedDockItem : CommandItem
+{
+    public override string Title => _itemTitle;
+
+    public override IIconInfo? Icon => _icon;
+
+    public override ICommand? Command => _backingList;
+
+    private readonly string _itemTitle;
+    private readonly IIconInfo? _icon;
+    private readonly WrappedDockList _backingList;
+
+    public IListItem[] Items { get => _backingList.GetItems(); set => _backingList.SetItems(value); }
+
+    public WrappedDockItem(
+        ICommand command,
+        string displayTitle)
+    {
+        _backingList = new WrappedDockList(command);
+        _itemTitle = string.IsNullOrEmpty(displayTitle) ? command.Name : displayTitle;
+        _icon = command.Icon;
+    }
+
+    public WrappedDockItem(
+        ICommandItem item,
+        string id,
+        string displayTitle)
+    {
+        _backingList = new WrappedDockList(item, id);
+        _itemTitle = string.IsNullOrEmpty(displayTitle) ? item.Title : displayTitle;
+        _icon = item.Icon;
+    }
+
+    public WrappedDockItem(IListItem[] items, string id, string displayTitle)
+    {
+        _backingList = new WrappedDockList(items, id, displayTitle);
+        _itemTitle = displayTitle;
+    }
+}
+
+public partial class WrappedDockList : ListPage
+{
+    private string _id;
+
+    public override string Id => _id;
+
+    // private ICommand _command;
+    private List<IListItem> _items;
+
+    public WrappedDockList(ICommand command)
+    {
+        // _command = command;
+        _items = new() { new ListItem(command) };
+        Name = command.Name;
+        _id = command.Id;
+    }
+
+    public WrappedDockList(ICommandItem item, string id)
+    {
+        var command = item.Command;
+
+        // TODO! This isn't _totally correct, because the wrapping item will not
+        // listen for property changes on the inner item.
+        _items = new()
+        {
+            new ListItem(command)
+            {
+                Title = item.Title,
+                Subtitle = item.Subtitle,
+                Icon = item.Icon,
+                MoreCommands = item.MoreCommands,
+            },
+        };
+        Name = command.Name;
+        _id = string.IsNullOrEmpty(id) ? command.Id : id;
+    }
+
+    public WrappedDockList(IListItem[] items, string id, string name)
+    {
+        _items = new(items);
+        Name = name;
+        _id = id;
+    }
+
+    public WrappedDockList(ICommand[] items, string id, string name)
+    {
+        _items = new();
+        foreach (var item in items)
+        {
+            _items.Add(new ListItem(item));
+        }
+
+        Name = name;
+        _id = id;
+    }
+
+    public override IListItem[] GetItems()
+    {
+        return _items.ToArray();
+    }
+
+    internal void SetItems(IListItem[]? newItems)
+    {
+        if (newItems == null)
+        {
+            _items = [];
+            RaiseItemsChanged(0);
+            return;
+        }
+
+        ListHelpers.InPlaceUpdateList(_items, newItems);
+        RaiseItemsChanged(_items.Count);
+    }
+}
+
+#pragma warning restore SA1402 // File may only contain a single type

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/FallbackCommandItem.cs

@@ -4,25 +4,18 @@
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
-public partial class FallbackCommandItem : CommandItem, IFallbackCommandItem, IFallbackHandler, IFallbackCommandItem2
+public partial class FallbackCommandItem : CommandItem, IFallbackCommandItem, IFallbackHandler
 {
     private readonly IFallbackHandler? _fallbackHandler;
 
-    public FallbackCommandItem(string displayTitle, string id)
+    public FallbackCommandItem(string displayTitle)
     {
         DisplayTitle = displayTitle;
-        Id = id;
     }
 
-    public FallbackCommandItem(ICommand command, string displayTitle, string id)
+    public FallbackCommandItem(ICommand command, string displayTitle)
         : base(command)
     {
-        if (string.IsNullOrWhiteSpace(id))
-        {
-            throw new ArgumentException("A non-empty or whitespace Id must be provided.", nameof(id));
-        }
-
-        Id = id;
         DisplayTitle = displayTitle;
         if (command is IFallbackHandler f)
         {
@@ -36,8 +29,6 @@ public partial class FallbackCommandItem : CommandItem, IFallbackCommandItem, IF
         init => _fallbackHandler = value;
     }
 
-    public virtual string Id { get; }
-
     public virtual string DisplayTitle { get; }
 
     public virtual void UpdateQuery(string query) => _fallbackHandler?.UpdateQuery(query);

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Filter.cs

@@ -6,9 +6,39 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class Filter : BaseObservable, IFilter
 {
-    public virtual IIconInfo Icon { get; set => SetProperty(ref field, value); } = new IconInfo();
+    public virtual IIconInfo Icon
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Icon));
+        }
+    }
 
-    public virtual string Id { get; set => SetProperty(ref field, value); } = string.Empty;
+= new IconInfo();
 
-    public virtual string Name { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Id
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Id));
+        }
+    }
+
+= string.Empty;
+
+    public virtual string Name
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Name));
+        }
+    }
+
+= string.Empty;
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Filters.cs

@@ -6,7 +6,17 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public abstract partial class Filters : BaseObservable, IFilters
 {
-    public string CurrentFilterId { get; set => SetProperty(ref field, value); } = string.Empty;
+    public string CurrentFilterId
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(CurrentFilterId));
+        }
+    }
+
+    = string.Empty;
 
     // This method should be overridden in derived classes to provide the actual filters.
     public abstract IFilterItem[] GetFilters();

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/FormContent.cs

@@ -6,11 +6,41 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class FormContent : BaseObservable, IFormContent
 {
-    public virtual string DataJson { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string DataJson
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(DataJson));
+        }
+    }
 
-    public virtual string StateJson { get; set => SetProperty(ref field, value); } = string.Empty;
+= string.Empty;
 
-    public virtual string TemplateJson { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string StateJson
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(StateJson));
+        }
+    }
+
+= string.Empty;
+
+    public virtual string TemplateJson
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(TemplateJson));
+        }
+    }
+
+= string.Empty;
 
     public virtual ICommandResult SubmitForm(string inputs, string data) => SubmitForm(inputs);
 

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/GalleryGridLayout.cs

@@ -6,7 +6,27 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class GalleryGridLayout : BaseObservable, IGalleryGridLayout
 {
-    public virtual bool ShowTitle { get; set => SetProperty(ref field, value); } = true;
+    public virtual bool ShowTitle
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(ShowTitle));
+        }
+    }
 
-    public virtual bool ShowSubtitle { get; set => SetProperty(ref field, value); } = true;
+    = true;
+
+    public virtual bool ShowSubtitle
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(ShowSubtitle));
+        }
+    }
+
+    = true;
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/IconData.cs

@@ -2,6 +2,7 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics.CodeAnalysis;
 using Windows.Storage.Streams;
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/ListItem.cs

@@ -1,18 +1,56 @@
-// Copyright (c) Microsoft Corporation
+// Copyright (c) Microsoft Corporation
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
-public partial class ListItem : CommandItem, IListItem
+public partial class ListItem : CommandItem, IListItem, IExtendedAttributesProvider
 {
-    public virtual ITag[] Tags { get; set => SetProperty(ref field, value); } = [];
+    private ITag[] _tags = [];
+    private IDetails? _details;
 
-    public virtual IDetails? Details { get; set => SetProperty(ref field, value); }
+    private string _section = string.Empty;
+    private string _textToSuggest = string.Empty;
 
-    public virtual string Section { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual ITag[] Tags
+    {
+        get => _tags;
+        set
+        {
+            _tags = value;
+            OnPropertyChanged(nameof(Tags));
+        }
+    }
 
-    public virtual string TextToSuggest { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual IDetails? Details
+    {
+        get => _details;
+        set
+        {
+            _details = value;
+            OnPropertyChanged(nameof(Details));
+        }
+    }
+
+    public virtual string Section
+    {
+        get => _section;
+        set
+        {
+            _section = value;
+            OnPropertyChanged(nameof(Section));
+        }
+    }
+
+    public virtual string TextToSuggest
+    {
+        get => _textToSuggest;
+        set
+        {
+            _textToSuggest = value;
+            OnPropertyChanged(nameof(TextToSuggest));
+        }
+    }
 
     public ListItem(ICommand command)
         : base(command)

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/ListPage.cs

@@ -8,23 +8,85 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class ListPage : Page, IListPage
 {
+    private string _placeholderText = string.Empty;
+    private string _searchText = string.Empty;
+    private bool _showDetails;
+    private bool _hasMore;
+    private IFilters? _filters;
+    private IGridProperties? _gridProperties;
+    private ICommandItem? _emptyContent;
+
     public event TypedEventHandler<object, IItemsChangedEventArgs>? ItemsChanged;
 
-    private string _searchText = string.Empty;
+    public virtual string PlaceholderText
+    {
+        get => _placeholderText;
+        set
+        {
+            _placeholderText = value;
+            OnPropertyChanged(nameof(PlaceholderText));
+        }
+    }
 
-    public virtual string PlaceholderText { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string SearchText
+    {
+        get => _searchText;
+        set
+        {
+            _searchText = value;
+            OnPropertyChanged(nameof(SearchText));
+        }
+    }
 
-    public virtual string SearchText { get => _searchText; set => SetProperty(ref _searchText, value); }
+    public virtual bool ShowDetails
+    {
+        get => _showDetails;
+        set
+        {
+            _showDetails = value;
+            OnPropertyChanged(nameof(ShowDetails));
+        }
+    }
 
-    public virtual bool ShowDetails { get; set => SetProperty(ref field, value); }
+    public virtual bool HasMoreItems
+    {
+        get => _hasMore;
+        set
+        {
+            _hasMore = value;
+            OnPropertyChanged(nameof(HasMoreItems));
+        }
+    }
 
-    public virtual bool HasMoreItems { get; set => SetProperty(ref field, value); }
+    public virtual IFilters? Filters
+    {
+        get => _filters;
+        set
+        {
+            _filters = value;
+            OnPropertyChanged(nameof(Filters));
+        }
+    }
 
-    public virtual IFilters? Filters { get; set => SetProperty(ref field, value); }
+    public virtual IGridProperties? GridProperties
+    {
+        get => _gridProperties;
+        set
+        {
+            _gridProperties = value;
+            OnPropertyChanged(nameof(GridProperties));
+        }
+    }
 
-    public virtual IGridProperties? GridProperties { get; set => SetProperty(ref field, value); }
-
-    public virtual ICommandItem? EmptyContent { get; set => SetProperty(ref field, value); }
+    public virtual ICommandItem? EmptyContent
+    {
+        get => _emptyContent;
+        set
+        {
+            _emptyContent = value;
+            OnPropertyChanged(nameof(EmptyContent));
+        }
+    }
 
     public virtual IListItem[] GetItems() => [];
 

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/MarkdownContent.cs

@@ -6,7 +6,17 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class MarkdownContent : BaseObservable, IMarkdownContent
 {
-    public virtual string Body { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Body
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Body));
+        }
+    }
+
+= string.Empty;
 
     public MarkdownContent()
     {

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/MediumGridLayout.cs

@@ -6,5 +6,15 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class MediumGridLayout : BaseObservable, IMediumGridLayout
 {
-    public virtual bool ShowTitle { get; set => SetProperty(ref field, value); } = true;
+    public virtual bool ShowTitle
+    {
+        get => field;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(ShowTitle));
+        }
+    }
+
+    = true;
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Page.cs

@@ -6,9 +6,37 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class Page : Command, IPage
 {
-    public virtual bool IsLoading { get; set => SetProperty(ref field, value); }
+    private bool _loading;
+    private string _title = string.Empty;
+    private OptionalColor _accentColor;
 
-    public virtual string Title { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual bool IsLoading
+    {
+        get => _loading;
+        set
+        {
+            _loading = value;
+            OnPropertyChanged(nameof(IsLoading));
+        }
+    }
 
-    public virtual OptionalColor AccentColor { get; set => SetProperty(ref field, value); }
+    public virtual string Title
+    {
+        get => _title;
+        set
+        {
+            _title = value;
+            OnPropertyChanged(nameof(Title));
+        }
+    }
+
+    public virtual OptionalColor AccentColor
+    {
+        get => _accentColor;
+        set
+        {
+            _accentColor = value;
+            OnPropertyChanged(nameof(AccentColor));
+        }
+    }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/ProgressState.cs

@@ -6,7 +6,27 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class ProgressState : BaseObservable, IProgressState
 {
-    public virtual bool IsIndeterminate { get; set => SetProperty(ref field, value); }
+    private bool _isIndeterminate;
 
-    public virtual uint ProgressPercent { get; set => SetProperty(ref field, value); }
+    private uint _progressPercent;
+
+    public virtual bool IsIndeterminate
+    {
+        get => _isIndeterminate;
+        set
+        {
+            _isIndeterminate = value;
+            OnPropertyChanged(nameof(IsIndeterminate));
+        }
+    }
+
+    public virtual uint ProgressPercent
+    {
+        get => _progressPercent;
+        set
+        {
+            _progressPercent = value;
+            OnPropertyChanged(nameof(ProgressPercent));
+        }
+    }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/PropChangedEventArgs.cs

@@ -2,6 +2,8 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using Windows.Foundation;
+
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class PropChangedEventArgs : IPropChangedEventArgs

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Section.cs

@@ -12,6 +12,11 @@ public sealed partial class Section : IEnumerable<IListItem>
 
     public string SectionTitle { get; set; } = string.Empty;
 
+    private Separator CreateSectionListItem()
+    {
+        return new Separator(SectionTitle);
+    }
+
     public Section(string sectionName, IListItem[] items)
     {
         SectionTitle = sectionName;
@@ -28,11 +33,6 @@ public sealed partial class Section : IEnumerable<IListItem>
     {
     }
 
-    private Separator CreateSectionListItem()
-    {
-        return new Separator(SectionTitle);
-    }
-
     public IEnumerator<IListItem> GetEnumerator() => Items.ToList().GetEnumerator();
 
     IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Separator.cs

@@ -4,8 +4,15 @@
 
 namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
-public partial class Separator : BaseObservable, IListItem, ISeparatorContextItem, ISeparatorFilterItem
+public partial class Separator : IListItem, ISeparatorContextItem, ISeparatorFilterItem
 {
+    public Separator(string? title = "")
+        : base()
+    {
+        Section = title ?? string.Empty;
+        Command = null;
+    }
+
     public IDetails? Details => null;
 
     public string? Section { get; private set; }
@@ -14,7 +21,7 @@ public partial class Separator : BaseObservable, IListItem, ISeparatorContextIte
 
     public string? TextToSuggest => null;
 
-    public ICommand? Command => null;
+    public ICommand? Command { get; private set; }
 
     public IIconInfo? Icon => null;
 
@@ -25,19 +32,12 @@ public partial class Separator : BaseObservable, IListItem, ISeparatorContextIte
     public string? Title
     {
         get => Section;
-        set
-        {
-            if (Section != value)
-            {
-                Section = value;
-                OnPropertyChanged();
-                OnPropertyChanged(Section);
-            }
-        }
+        set => Section = value;
     }
 
-    public Separator(string? title = "")
+    public event Windows.Foundation.TypedEventHandler<object, IPropChangedEventArgs>? PropChanged
     {
-        Section = title ?? string.Empty;
+        add { }
+        remove { }
     }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/StatusMessage.cs

@@ -6,9 +6,37 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class StatusMessage : BaseObservable, IStatusMessage
 {
-    public virtual string Message { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual string Message
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Message));
+        }
+    }
 
-    public virtual MessageState State { get; set => SetProperty(ref field, value); } = MessageState.Info;
+= string.Empty;
 
-    public virtual IProgressState? Progress { get; set => SetProperty(ref field, value); }
+    public virtual MessageState State
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(State));
+        }
+    }
+
+= MessageState.Info;
+
+    public virtual IProgressState? Progress
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Progress));
+        }
+    }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/Tag.cs

@@ -6,15 +6,63 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class Tag : BaseObservable, ITag
 {
-    public virtual OptionalColor Foreground { get; set => SetProperty(ref field, value); }
+    private OptionalColor _foreground;
+    private OptionalColor _background;
+    private string _text = string.Empty;
 
-    public virtual OptionalColor Background { get; set => SetProperty(ref field, value); }
+    public virtual OptionalColor Foreground
+    {
+        get => _foreground;
+        set
+        {
+            _foreground = value;
+            OnPropertyChanged(nameof(Foreground));
+        }
+    }
 
-    public virtual IIconInfo Icon { get; set => SetProperty(ref field, value); } = new IconInfo();
+    public virtual OptionalColor Background
+    {
+        get => _background;
+        set
+        {
+            _background = value;
+            OnPropertyChanged(nameof(Background));
+        }
+    }
 
-    public virtual string Text { get; set => SetProperty(ref field, value); } = string.Empty;
+    public virtual IIconInfo Icon
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(Icon));
+        }
+    }
 
-    public virtual string ToolTip { get; set => SetProperty(ref field, value); } = string.Empty;
+= new IconInfo();
+
+    public virtual string Text
+    {
+        get => _text;
+        set
+        {
+            _text = value;
+            OnPropertyChanged(nameof(Text));
+        }
+    }
+
+    public virtual string ToolTip
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(ToolTip));
+        }
+    }
+
+= string.Empty;
 
     public Tag()
     {
@@ -22,6 +70,6 @@ public partial class Tag : BaseObservable, ITag
 
     public Tag(string text)
     {
-        Text = text;
+        _text = text;
     }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/TreeContent.cs

@@ -8,11 +8,19 @@ namespace Microsoft.CommandPalette.Extensions.Toolkit;
 
 public partial class TreeContent : BaseObservable, ITreeContent
 {
-    public event TypedEventHandler<object, IItemsChangedEventArgs>? ItemsChanged;
-
     public IContent[] Children { get; set; } = [];
 
-    public virtual IContent? RootContent { get; set => SetProperty(ref field, value); }
+    public virtual IContent? RootContent
+    {
+        get;
+        set
+        {
+            field = value;
+            OnPropertyChanged(nameof(RootContent));
+        }
+    }
+
+    public event TypedEventHandler<object, IItemsChangedEventArgs>? ItemsChanged;
 
     public virtual IContent[] GetChildren() => Children;
 

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions/Microsoft.CommandPalette.Extensions.idl

@@ -371,11 +371,6 @@ namespace Microsoft.CommandPalette.Extensions
         IFallbackHandler FallbackHandler{ get; };
         String DisplayTitle { get; };
     };
-
-    [contract(Microsoft.CommandPalette.Extensions.ExtensionsContract, 1)]
-    interface IFallbackCommandItem2 requires IFallbackCommandItem {
-        String Id { get; };
-    };
     
     [contract(Microsoft.CommandPalette.Extensions.ExtensionsContract, 1)]
     interface ICommandProvider requires Windows.Foundation.IClosable, INotifyItemsChanged