dotnet · danmoseley · Aug 20, 2020 · Aug 19, 2020
diff --git a/eng/DefaultGenApiDocIds.txt b/eng/DefaultGenApiDocIds.txt
@@ -1,10 +1,7 @@
 // These attributes should be excluded from reference assemblies.
 
-T:System.ComponentModel.Design.Serialization.DesignerSerializerAttribute
 T:System.ComponentModel.Design.Serialization.RootDesignerSerializerAttribute
 T:System.ComponentModel.EditorAttribute
-T:System.ComponentModel.ToolboxItemAttribute
-T:System.ComponentModel.TypeDescriptionProviderAttribute
 T:System.Configuration.ConfigurationPropertyAttribute
 T:System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute
 T:System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverageAttribute

diff --git a/src/libraries/System.CodeDom/ref/System.CodeDom.cs b/src/libraries/System.CodeDom/ref/System.CodeDom.cs
@@ -875,6 +875,7 @@ protected CodeCompiler() { }
         System.CodeDom.Compiler.CompilerResults System.CodeDom.Compiler.ICodeCompiler.CompileAssemblyFromSource(System.CodeDom.Compiler.CompilerParameters options, string source) { throw null; }
         System.CodeDom.Compiler.CompilerResults System.CodeDom.Compiler.ICodeCompiler.CompileAssemblyFromSourceBatch(System.CodeDom.Compiler.CompilerParameters options, string[] sources) { throw null; }
     }
+    [System.ComponentModel.ToolboxItemAttribute(false)]
     public abstract partial class CodeDomProvider : System.ComponentModel.Component
     {
         protected CodeDomProvider() { }

diff --git a/src/libraries/System.CodeDom/src/System/CodeDom/Compiler/CodeDomProvider.cs b/src/libraries/System.CodeDom/src/System/CodeDom/Compiler/CodeDomProvider.cs
@@ -10,6 +10,7 @@
 
 namespace System.CodeDom.Compiler
 {
+    [ToolboxItem(false)]
     public abstract class CodeDomProvider : Component
     {
         private static readonly Dictionary<string, CompilerInfo> s_compilerLanguages = new Dictionary<string, CompilerInfo>(StringComparer.OrdinalIgnoreCase);

diff --git a/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs b/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs
@@ -219,6 +219,7 @@ void System.Collections.ICollection.CopyTo(System.Array array, int index) { }
         void System.Collections.IList.Insert(int index, object? value) { }
         void System.Collections.IList.Remove(object? value) { }
     }
+    [System.ComponentModel.Design.Serialization.DesignerSerializerAttribute("System.Diagnostics.Design.StringDictionaryCodeDomSerializer, System.Design, Version=4.0.0.0, PublicKeyToken=b03f5f7f11d50a3a", "System.ComponentModel.Design.Serialization.CodeDomSerializer, System.Design, Version=4.0.0.0, PublicKeyToken=b03f5f7f11d50a3a")]
     public partial class StringDictionary : System.Collections.IEnumerable
     {
         public StringDictionary() { }

diff --git a/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.csproj b/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.csproj
@@ -9,6 +9,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\System.Runtime\ref\System.Runtime.csproj" />
     <ProjectReference Include="..\..\System.Runtime.Extensions\ref\System.Runtime.Extensions.csproj" />
+    <ProjectReference Include="..\..\System.ComponentModel.Primitives\ref\System.ComponentModel.Primitives.csproj" />
     <ProjectReference Include="..\..\System.Collections.NonGeneric\ref\System.Collections.NonGeneric.csproj" />
   </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Collections.Specialized/src/System.Collections.Specialized.csproj b/src/libraries/System.Collections.Specialized/src/System.Collections.Specialized.csproj
@@ -18,6 +18,7 @@
   </ItemGroup>
   <ItemGroup>
     <Reference Include="System.Collections.NonGeneric" />
+    <Reference Include="System.ComponentModel.Primitives" />
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Threading" />

diff --git a/...ies/System.Collections.Specialized/src/System/Collections/Specialized/StringDictionary.cs b/...ies/System.Collections.Specialized/src/System/Collections/Specialized/StringDictionary.cs
@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 
+using System.ComponentModel.Design.Serialization;
+
 namespace System.Collections.Specialized
 {
     /// <devdoc>
@@ -12,6 +14,8 @@ namespace System.Collections.Specialized
     /// </devdoc>
     [Serializable]
     [System.Runtime.CompilerServices.TypeForwardedFrom("System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    [DesignerSerializer("System.Diagnostics.Design.StringDictionaryCodeDomSerializer, System.Design, Version=4.0.0.0, PublicKeyToken=b03f5f7f11d50a3a",
+                        "System.ComponentModel.Design.Serialization.CodeDomSerializer, System.Design, Version=4.0.0.0, PublicKeyToken=b03f5f7f11d50a3a")]
     public class StringDictionary : IEnumerable
     {
         // For compatibility, we want the Keys property to return values in lower-case.

diff --git a/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs b/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs
@@ -312,3 +312,16 @@ public RefreshPropertiesAttribute(System.ComponentModel.RefreshProperties refres
         public override bool IsDefaultAttribute() { throw null; }
     }
 }
+namespace System.ComponentModel.Design.Serialization
+{
+    [System.AttributeUsageAttribute(System.AttributeTargets.Class | System.AttributeTargets.Interface, AllowMultiple=true, Inherited=true)]
+    public sealed partial class DesignerSerializerAttribute : System.Attribute
+    {
+        public DesignerSerializerAttribute(string serializerTypeName, string baseSerializerTypeName) { }
+        public DesignerSerializerAttribute(string serializerTypeName, System.Type baseSerializerType) { }
+        public DesignerSerializerAttribute(System.Type serializerType, System.Type baseSerializerType) { }
+        public string? SerializerBaseTypeName { get { throw null; } }
+        public string? SerializerTypeName { get { throw null; } }
+        public override object TypeId { get { throw null; } }
+    }
+}
diff --git a/src/libraries/System.ComponentModel.Primitives/src/System.ComponentModel.Primitives.csproj b/src/libraries/System.ComponentModel.Primitives/src/System.ComponentModel.Primitives.csproj
@@ -15,6 +15,7 @@
     <Compile Include="System\ComponentModel\DesignerSerializationVisibility.cs" />
     <Compile Include="System\ComponentModel\DesignerSerializationVisibilityAttribute.cs" />
     <Compile Include="System\ComponentModel\DesignOnlyAttribute.cs" />
+    <Compile Include="System\ComponentModel\Design\Serialization\DesignerSerializerAttribute.cs" />
     <Compile Include="System\ComponentModel\DisplayNameAttribute.cs" />
     <Compile Include="System\ComponentModel\EventHandlerList.cs" />
     <Compile Include="System\ComponentModel\IComponent.cs" />

diff --git a/...ialization/DesignerSerializerAttribute.cs → ...ialization/DesignerSerializerAttribute.cs b/...ialization/DesignerSerializerAttribute.cs → ...ialization/DesignerSerializerAttribute.cs
@@ -11,7 +11,7 @@ namespace System.ComponentModel.Design.Serialization
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = true, Inherited = true)]
     public sealed class DesignerSerializerAttribute : Attribute
     {
-        private string _typeId;
+        private string? _typeId;
 
         /// <summary>
         /// Creates a new designer serialization attribute.
@@ -34,7 +34,7 @@ public DesignerSerializerAttribute(Type serializerType, Type baseSerializerType)
         /// <summary>
         /// Creates a new designer serialization attribute.
         /// </summary>
-        public DesignerSerializerAttribute(string serializerTypeName, Type baseSerializerType)
+        public DesignerSerializerAttribute(string? serializerTypeName, Type baseSerializerType)
         {
             if (baseSerializerType == null)
             {
@@ -48,7 +48,7 @@ public DesignerSerializerAttribute(string serializerTypeName, Type baseSerialize
         /// <summary>
         /// Creates a new designer serialization attribute.
         /// </summary>
-        public DesignerSerializerAttribute(string serializerTypeName, string baseSerializerTypeName)
+        public DesignerSerializerAttribute(string? serializerTypeName, string? baseSerializerTypeName)
         {
             SerializerTypeName = serializerTypeName;
             SerializerBaseTypeName = baseSerializerTypeName;
@@ -57,12 +57,12 @@ public DesignerSerializerAttribute(string serializerTypeName, string baseSeriali
         /// <summary>
         /// Retrieves the fully qualified type name of the serializer.
         /// </summary>
-        public string SerializerTypeName { get; }
+        public string? SerializerTypeName { get; }
 
         /// <summary>
         /// Retrieves the fully qualified type name of the serializer base type.
         /// </summary>
-        public string SerializerBaseTypeName { get; }
+        public string? SerializerBaseTypeName { get; }
 
         /// <summary>
         /// This defines a unique ID for this attribute type. It is used

diff --git a/...ation/DesignerSerializerAttributeTests.cs → ...ation/DesignerSerializerAttributeTests.cs b/...ation/DesignerSerializerAttributeTests.cs → ...ation/DesignerSerializerAttributeTests.cs
diff --git a/...s/System.ComponentModel.TypeConverter/ref/System.ComponentModel.TypeConverter.Forwards.cs b/...s/System.ComponentModel.TypeConverter/ref/System.ComponentModel.TypeConverter.Forwards.cs
@@ -6,6 +6,7 @@
 
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.Component))]
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.DesignerAttribute))]
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.Design.Serialization.DesignerSerializerAttribute))]
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.InvalidAsynchronousStateException))]
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.InvalidEnumArgumentException))]
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.ComponentModel.ISupportInitialize))]

diff --git a/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.TypeConverter.cs b/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.TypeConverter.cs
@@ -2052,16 +2052,6 @@ protected DesignerLoader() { }
         public abstract void Dispose();
         public virtual void Flush() { }
     }
-    [System.AttributeUsageAttribute(System.AttributeTargets.Class | System.AttributeTargets.Interface, AllowMultiple=true, Inherited=true)]
-    public sealed partial class DesignerSerializerAttribute : System.Attribute
-    {
-        public DesignerSerializerAttribute(string serializerTypeName, string baseSerializerTypeName) { }
-        public DesignerSerializerAttribute(string serializerTypeName, System.Type baseSerializerType) { }
-        public DesignerSerializerAttribute(System.Type serializerType, System.Type baseSerializerType) { }
-        public string SerializerBaseTypeName { get { throw null; } }
-        public string SerializerTypeName { get { throw null; } }
-        public override object TypeId { get { throw null; } }
-    }
     public partial interface IDesignerLoaderHost : System.ComponentModel.Design.IDesignerHost, System.ComponentModel.Design.IServiceContainer, System.IServiceProvider
     {
         void EndLoad(string baseClassName, bool successful, System.Collections.ICollection errorCollection);

diff --git a/...raries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj b/...raries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj
@@ -220,7 +220,6 @@
     <Compile Include="System\ComponentModel\Design\Serialization\ContextStack.cs" />
     <Compile Include="System\ComponentModel\Design\Serialization\DefaultSerializationProviderAttribute.cs" />
     <Compile Include="System\ComponentModel\Design\Serialization\DesignerLoader.cs" />
-    <Compile Include="System\ComponentModel\Design\Serialization\DesignerSerializerAttribute.cs" />
     <Compile Include="System\ComponentModel\Design\Serialization\SerializationStore.cs" />
     <Compile Include="System\ComponentModel\Design\Serialization\IDesignerLoaderHost.cs" />
     <Compile Include="System\ComponentModel\Design\Serialization\IDesignerLoaderService.cs" />

diff --git a/...ystem.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj b/...ystem.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj
@@ -83,7 +83,6 @@
     <Compile Include="Design\Serialization\RootDesignerSerializerAttributeTests.cs" />
     <Compile Include="Design\Serialization\ResolveNameEventArgsTests.cs" />
     <Compile Include="Design\Serialization\MemberRelationshipTests.cs" />
-    <Compile Include="Design\Serialization\DesignerSerializerAttributeTests.cs" />
     <Compile Include="Design\Serialization\DesignerLoaderTests.cs" />
     <Compile Include="Design\Serialization\DefaultSerializationProviderAttributeTests.cs" />
     <Compile Include="Design\MenuCommandTests.cs" />

diff --git a/src/libraries/System.Data.Common/ref/System.Data.Common.cs b/src/libraries/System.Data.Common/ref/System.Data.Common.cs
@@ -471,8 +471,9 @@ public void EndEdit() { }
         object System.ComponentModel.ICustomTypeDescriptor.GetPropertyOwner(System.ComponentModel.PropertyDescriptor pd) { throw null; }
 #nullable enable
     }
-    [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.DataSetDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     [System.ComponentModel.DefaultPropertyAttribute("DataSetName")]
+    [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.DataSetDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [System.ComponentModel.ToolboxItemAttribute("Microsoft.VSDesigner.Data.VS.DataSetToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     [System.Xml.Serialization.XmlRootAttribute("DataSet")]
     [System.Xml.Serialization.XmlSchemaProviderAttribute("GetDataSetSchema")]
     public partial class DataSet : System.ComponentModel.MarshalByValueComponent, System.ComponentModel.IListSource, System.ComponentModel.ISupportInitialize, System.ComponentModel.ISupportInitializeNotification, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable

diff --git a/src/libraries/System.Data.Common/src/System/Data/DataSet.cs b/src/libraries/System.Data.Common/src/System/Data/DataSet.cs
@@ -26,6 +26,7 @@ namespace System.Data
     [Designer("Microsoft.VSDesigner.Data.VS.DataSetDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     [DefaultProperty(nameof(DataSetName))]
     [Serializable]
+    [ToolboxItem("Microsoft.VSDesigner.Data.VS.DataSetToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     [XmlSchemaProvider(nameof(GetDataSetSchema))]
     [XmlRoot(nameof(DataSet))]
     [System.Runtime.CompilerServices.TypeForwardedFrom("System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]

diff --git a/src/libraries/System.Data.Odbc/ref/System.Data.Odbc.cs b/src/libraries/System.Data.Odbc/ref/System.Data.Odbc.cs
@@ -7,6 +7,7 @@
 namespace System.Data.Odbc
 {
     [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.OdbcCommandDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [System.ComponentModel.ToolboxItemAttribute(true)]
     public sealed partial class OdbcCommand : System.Data.Common.DbCommand, System.ICloneable
     {
         public OdbcCommand() { }
@@ -125,6 +126,7 @@ public override void Clear() { }
         public override bool TryGetValue(string keyword, [System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out object? value) { throw null; }
     }
     [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.OdbcDataAdapterDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [System.ComponentModel.ToolboxItemAttribute("Microsoft.VSDesigner.Data.VS.OdbcDataAdapterToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     public sealed partial class OdbcDataAdapter : System.Data.Common.DbDataAdapter, System.Data.IDataAdapter, System.Data.IDbDataAdapter, System.ICloneable
     {
         public OdbcDataAdapter() { }

diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs
@@ -17,6 +17,7 @@
 namespace System.Data.Odbc
 {
     [Designer("Microsoft.VSDesigner.Data.VS.OdbcCommandDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [ToolboxItem(true)]
     public sealed class OdbcCommand : DbCommand, ICloneable
     {
         private static int s_objectTypeCount; // Bid counter

diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataAdapter.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataAdapter.cs
@@ -7,6 +7,7 @@
 namespace System.Data.Odbc
 {
     [Designer("Microsoft.VSDesigner.Data.VS.OdbcDataAdapterDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [ToolboxItem("Microsoft.VSDesigner.Data.VS.OdbcDataAdapterToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     public sealed class OdbcDataAdapter : DbDataAdapter, IDbDataAdapter, ICloneable
     {
         private static readonly object s_eventRowUpdated = new object();

diff --git a/src/libraries/System.Data.OleDb/ref/System.Data.OleDb.cs b/src/libraries/System.Data.OleDb/ref/System.Data.OleDb.cs
@@ -7,6 +7,7 @@
 namespace System.Data.OleDb
 {
     [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.OleDbCommandDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [System.ComponentModel.ToolboxItemAttribute(true)]
     public sealed partial class OleDbCommand : System.Data.Common.DbCommand, System.Data.IDbCommand, System.ICloneable, System.IDisposable
     {
         public OleDbCommand() { }
@@ -142,6 +143,7 @@ public override void Clear() { }
         public override bool TryGetValue(string keyword, [System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out object? value) { throw null; }
     }
     [System.ComponentModel.DesignerAttribute("Microsoft.VSDesigner.Data.VS.OleDbDataAdapterDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [System.ComponentModel.ToolboxItemAttribute("Microsoft.VSDesigner.Data.VS.OleDbDataAdapterToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     public sealed partial class OleDbDataAdapter : System.Data.Common.DbDataAdapter, System.Data.IDataAdapter, System.Data.IDbDataAdapter, System.ICloneable
     {
         public OleDbDataAdapter() { }

diff --git a/src/libraries/System.Data.OleDb/src/OleDbCommand.cs b/src/libraries/System.Data.OleDb/src/OleDbCommand.cs
@@ -13,6 +13,7 @@
 namespace System.Data.OleDb
 {
     [Designer("Microsoft.VSDesigner.Data.VS.OleDbCommandDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [ToolboxItem(true)]
     public sealed class OleDbCommand : DbCommand, ICloneable, IDbCommand
     {
         // command data

diff --git a/src/libraries/System.Data.OleDb/src/OleDbDataAdapter.cs b/src/libraries/System.Data.OleDb/src/OleDbDataAdapter.cs
@@ -9,6 +9,7 @@
 namespace System.Data.OleDb
 {
     [Designer("Microsoft.VSDesigner.Data.VS.OleDbDataAdapterDesigner, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
+    [ToolboxItem("Microsoft.VSDesigner.Data.VS.OleDbDataAdapterToolboxItem, Microsoft.VSDesigner, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     public sealed class OleDbDataAdapter : DbDataAdapter, IDbDataAdapter, ICloneable
     {
         private static readonly object EventRowUpdated = new object();

diff --git a/src/libraries/System.Windows.Extensions/ref/System.Windows.Extensions.cs b/src/libraries/System.Windows.Extensions/ref/System.Windows.Extensions.cs
@@ -6,6 +6,7 @@
 
 namespace System.Media
 {
+    [System.ComponentModel.ToolboxItemAttribute(false)]
     public partial class SoundPlayer : System.ComponentModel.Component, System.Runtime.Serialization.ISerializable
     {
         public SoundPlayer() { }

diff --git a/src/libraries/System.Windows.Extensions/src/System/Media/SoundPlayer.cs b/src/libraries/System.Windows.Extensions/src/System/Media/SoundPlayer.cs
@@ -12,6 +12,7 @@
 
 namespace System.Media
 {
+    [ToolboxItem(false)]
     public class SoundPlayer : Component, ISerializable
     {
         private const int BlockSize = 1024;

diff --git a/src/libraries/System.Xml.XDocument/ref/System.Xml.XDocument.cs b/src/libraries/System.Xml.XDocument/ref/System.Xml.XDocument.cs
@@ -48,6 +48,7 @@ public enum SaveOptions
         DisableFormatting = 1,
         OmitDuplicateNamespaces = 2,
     }
+    [System.ComponentModel.TypeDescriptionProviderAttribute("MS.Internal.Xml.Linq.ComponentModel.XTypeDescriptionProvider`1[[System.Xml.Linq.XAttribute, System.Xml.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]],System.ComponentModel.TypeConverter")]
     public partial class XAttribute : System.Xml.Linq.XObject
     {
         public XAttribute(System.Xml.Linq.XAttribute other) { }
@@ -209,6 +210,7 @@ public override void WriteTo(System.Xml.XmlWriter writer) { }
         public override System.Threading.Tasks.Task WriteToAsync(System.Xml.XmlWriter writer, System.Threading.CancellationToken cancellationToken) { throw null; }
     }
     [System.Xml.Serialization.XmlSchemaProviderAttribute(null, IsAny=true)]
+    [System.ComponentModel.TypeDescriptionProviderAttribute("MS.Internal.Xml.Linq.ComponentModel.XTypeDescriptionProvider`1[[System.Xml.Linq.XElement, System.Xml.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]],System.ComponentModel.TypeConverter")]
     public partial class XElement : System.Xml.Linq.XContainer, System.Xml.Serialization.IXmlSerializable
     {
         public XElement(System.Xml.Linq.XElement other) { }

diff --git a/src/libraries/System.Xml.XDocument/ref/System.Xml.XDocument.csproj b/src/libraries/System.Xml.XDocument/ref/System.Xml.XDocument.csproj
@@ -6,6 +6,7 @@
     <Compile Include="System.Xml.XDocument.cs" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\..\System.ObjectModel\ref\System.ObjectModel.csproj" />
     <ProjectReference Include="..\..\System.Runtime\ref\System.Runtime.csproj" />
     <ProjectReference Include="..\..\System.Runtime.Extensions\ref\System.Runtime.Extensions.csproj" />
     <ProjectReference Include="..\..\System.Xml.ReaderWriter\ref\System.Xml.ReaderWriter.csproj" />