add it back to the toolkit

src/modules/cmdpal/ext/SamplePagesExtension/Pages/SampleListPage.cs

@@ -229,42 +229,4 @@ internal sealed partial class SampleListPage : ListPage
             { "hmm?", null },
         };
     }
-
-    /// <summary>
-    /// Represents an icon that is a font glyph.
-    /// This is used for icons that are defined by a specific font face,
-    /// such as Wingdings.
-    ///
-    /// Note that Command Palette will default to using the Segoe Fluent Icons,
-    /// Segoe MDL2 Assets font for glyphs in the Segoe UI Symbol range, or Segoe
-    /// UI for any other glyphs. This class is only needed if you want a non-Segoe
-    /// font icon.
-    ///
-    /// WHY ISN'T THIS IN THE TOOLKIT: I have NO idea why, but if you put this
-    /// in the toolkit, and not in your extension code, we 100% fail to cast
-    /// the `Dictionary` to an IDictionary. The error was in
-    /// `IExtendedAttributesProvider:Do_Abi_GetProperties_0`
-    /// </summary>
-    internal sealed partial class FontIconData : IconData, IExtendedAttributesProvider
-    {
-        private string FontFamily { get; set; }
-
-        // LOAD-BEARING: Use a Windows.Foundation.Collections.ValueSet as the
-        // backing store for Properties. A regular `Dictionary<string, object>`
-        // will not work across the ABI
-        private readonly Windows.Foundation.Collections.ValueSet _properties;
-
-        public IDictionary<string, object> GetProperties() => _properties;
-
-        public FontIconData(string glyph, string fontFamily)
-            : base(glyph)
-        {
-            FontFamily = fontFamily;
-
-            _properties = new Windows.Foundation.Collections.ValueSet()
-            {
-                { "FontFamily", FontFamily },
-            };
-        }
-    }
 }

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

@@ -0,0 +1,32 @@
+// 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 Windows.Foundation.Collections;
+
+namespace Microsoft.CommandPalette.Extensions.Toolkit;
+
+/// <summary>
+/// Represents an icon that is a font glyph.
+/// This is used for icons that are defined by a specific font face,
+/// such as Wingdings.
+///
+/// Note that Command Palette will default to using the Segoe Fluent Icons,
+/// Segoe MDL2 Assets font for glyphs in the Segoe UI Symbol range, or Segoe
+/// UI for any other glyphs. This class is only needed if you want a non-Segoe
+/// font icon.
+/// </summary>
+public partial class FontIconData : IconData, IExtendedAttributesProvider
+{
+    public string FontFamily { get; set; }
+
+    public FontIconData(string glyph, string fontFamily)
+        : base(glyph)
+    {
+        FontFamily = fontFamily;
+    }
+
+    public IDictionary<string, object>? GetProperties() => new ValueSet()
+        {
+            { "FontFamily", FontFamily },
+        };
+}

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;