Use ReadOnlyCollection.Empty

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/ManipulationDevice.cs

@@ -215,7 +215,7 @@ internal IEnumerable<IManipulator> GetManipulatorsReadOnly()
             }
             else
             {
-                return new ReadOnlyCollection<IManipulator>(new List<IManipulator>(2));
+                return ReadOnlyCollection<IManipulator>.Empty;
             }
         }
 

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/ContainerParaClient.cs

@@ -330,7 +330,7 @@ internal ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out boo
 
             if (subtrackDetails.cParas == 0) 
             {
-                return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                return ReadOnlyCollection<ParagraphResult>.Empty;
             }
 
             // Get list of paragraphs

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/FigureParaClient.cs

@@ -571,7 +571,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
 
                 if (trackDetails.cParas == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));  
+                    return ReadOnlyCollection<ParagraphResult>.Empty;  
                 }
 
                 // Get list of paragraphs
@@ -597,7 +597,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
                 // cBasicColumns == 0, means that subpage content is empty
                 if (subpageDetails.u.complex.cBasicColumns == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                    return ReadOnlyCollection<ParagraphResult>.Empty;
                 }
 
                 // Retrieve description for each column.
@@ -611,7 +611,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
 
                 if (trackDetails.cParas == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                    return ReadOnlyCollection<ParagraphResult>.Empty;
                 }
 
                 // Get list of paragraphs
@@ -738,7 +738,7 @@ internal Geometry GetTightBoundingGeometryFromTextPositions(ReadOnlyCollection<C
             // Figure always has one column, so we can skip getting a column from the text position range
             Invariant.Assert(columns != null && columns.Count <= 1, "Columns collection is null.");
             Invariant.Assert(floatingElements != null, "Floating element collection is null.");
-            ReadOnlyCollection<ParagraphResult> paragraphs = (columns.Count > 0) ? columns[0].Paragraphs : new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+            ReadOnlyCollection<ParagraphResult> paragraphs = (columns.Count > 0) ? columns[0].Paragraphs : ReadOnlyCollection<ParagraphResult>.Empty;
 
             if (paragraphs.Count > 0 || floatingElements.Count > 0)
             {

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/FloaterParaClient.cs

@@ -580,7 +580,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
 
                 if (trackDetails.cParas == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));  
+                    return ReadOnlyCollection<ParagraphResult>.Empty;  
                 }
 
                 // Get list of paragraphs
@@ -606,7 +606,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
                 // cBasicColumns == 0, means that subpage content is empty
                 if (subpageDetails.u.complex.cBasicColumns == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                    return ReadOnlyCollection<ParagraphResult>.Empty;
                 }
 
                 // Retrieve description for each column.
@@ -620,7 +620,7 @@ private ReadOnlyCollection<ParagraphResult> GetChildrenParagraphResults(out bool
 
                 if (trackDetails.cParas == 0) 
                 {
-                    return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                    return ReadOnlyCollection<ParagraphResult>.Empty;
                 }
 
                 // Get list of paragraphs
@@ -747,7 +747,7 @@ internal Geometry GetTightBoundingGeometryFromTextPositions(ReadOnlyCollection<C
             // Floater always has one column, so we can skip getting a column from the text position range
             Invariant.Assert(columns != null && columns.Count <= 1, "Columns collection is null.");
             Invariant.Assert(floatingElements != null, "Floating element collection is null.");
-            ReadOnlyCollection<ParagraphResult> paragraphs = (columns.Count > 0) ? columns[0].Paragraphs : new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+            ReadOnlyCollection<ParagraphResult> paragraphs = (columns.Count > 0) ? columns[0].Paragraphs : ReadOnlyCollection<ParagraphResult>.Empty;
 
             if (paragraphs.Count > 0 || floatingElements.Count > 0)
             {

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/FlowDocumentPage.cs

@@ -367,7 +367,7 @@ internal IEnumerator<IInputElement> HostedElementsCore
                 else
                 {
                     // Return empty collection
-                    return new HostedElements(new ReadOnlyCollection<TextSegment>(new List<TextSegment>(0)));
+                    return new HostedElements(ReadOnlyCollection<TextSegment>.Empty);
                 }
             }
         }
@@ -572,7 +572,7 @@ internal ReadOnlyCollection<ParagraphResult> GetParagraphResultsFromColumn(IntPt
 
             if (trackDetails.cParas == 0)
             {
-                return new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+                return ReadOnlyCollection<ParagraphResult>.Empty;
             }
 
             PTS.FSPARADESCRIPTION[] arrayParaDesc;

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/PageVisual.cs

@@ -125,7 +125,7 @@ ReadOnlyCollection<Rect> IContentHost.GetRectangles(ContentElement child)
             {
                 return host.GetRectangles(child);
             }
-            return new ReadOnlyCollection<Rect>(new List<Rect>(0));
+            return ReadOnlyCollection<Rect>.Empty;
         }
 
         /// <summary>

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/PtsHost/TextParaClient.cs

@@ -339,7 +339,7 @@ internal ReadOnlyCollection<LineResult> GetLineResults()
 #if TEXTPANELLAYOUTDEBUG
             TextPanelDebug.IncrementCounter("TextPara.GetLines", TextPanelDebug.Category.TextView);
 #endif
-            ReadOnlyCollection<LineResult> lines = new ReadOnlyCollection<LineResult>(new List<LineResult>(0));
+            ReadOnlyCollection<LineResult> lines = ReadOnlyCollection<LineResult>.Empty;
 
             // Query paragraph details
             PTS.FSTEXTDETAILS textDetails;

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/DocumentPageTextView.cs

@@ -313,7 +313,7 @@ internal override ReadOnlyCollection<GlyphRun> GetGlyphRuns(ITextPointer start,
             }
             if (IsPageMissing)
             {
-                return new ReadOnlyCollection<GlyphRun>(new List<GlyphRun>());
+                return ReadOnlyCollection<GlyphRun>.Empty;
             }
             return _pageTextView.GetGlyphRuns(start, end);
         }
@@ -528,7 +528,7 @@ internal override ReadOnlyCollection<TextSegment> TextSegments
             {
                 if (!IsValid || IsPageMissing)
                 {
-                    return new ReadOnlyCollection<TextSegment>(new List<TextSegment>());
+                    return ReadOnlyCollection<TextSegment>.Empty;
                 }
                 return _pageTextView.TextSegments;
             }

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/TextDocumentView.cs

@@ -589,7 +589,7 @@ internal override ReadOnlyCollection<TextSegment> TextSegments
                 // Verify that layout information is valid. Cannot continue if not valid.
                 if (!IsValid)
                 {
-                    return new ReadOnlyCollection<TextSegment>(new List<TextSegment>());
+                    return ReadOnlyCollection<TextSegment>.Empty;
                 }
                 return this.TextSegmentsCore;
             }
@@ -3559,7 +3559,7 @@ private Rect GetRectangleFromContentEdge(ParagraphResult paragraphResult, ITextP
         /// <summary>
         /// Cached collection of ColumnResults.
         /// </summary>
-        private static ReadOnlyCollection<ParagraphResult> _emptyParagraphCollection = new ReadOnlyCollection<ParagraphResult>(new List<ParagraphResult>(0));
+        private static ReadOnlyCollection<ParagraphResult> _emptyParagraphCollection = ReadOnlyCollection<ParagraphResult>.Empty;
 
         /// <summary>
         /// Cached collection of TextSegments.

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/TextViewBase.cs

@@ -109,7 +109,7 @@ internal virtual ReadOnlyCollection<GlyphRun> GetGlyphRuns(ITextPointer start, I
             {
                 throw new InvalidOperationException(SR.TextViewInvalidLayout);
             }
-            return new ReadOnlyCollection<GlyphRun>(new List<GlyphRun>());
+            return ReadOnlyCollection<GlyphRun>.Empty;
         }
 
         /// <summary>

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/UIElementIsland.cs

@@ -195,7 +195,7 @@ IInputElement IContentHost.InputHitTest(Point point)
         /// </summary>
         ReadOnlyCollection<Rect> IContentHost.GetRectangles(ContentElement child)
         {
-            return new ReadOnlyCollection<Rect>(new List<Rect>());
+            return ReadOnlyCollection<Rect>.Empty;
         }
 
         /// <summary>

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Annotations/AnnotationDocumentPaginator.cs

@@ -447,7 +447,7 @@ public IEnumerator<IInputElement> HostedElements
                     }
                     else
                     {
-                        return new HostedElements(new ReadOnlyCollection<TextSegment>(new List<TextSegment>(0)));
+                        return new HostedElements(ReadOnlyCollection<TextSegment>.Empty);
                     }
                 }
             }
@@ -463,7 +463,7 @@ public ReadOnlyCollection<Rect> GetRectangles(ContentElement child)
                 }
                 else
                 {
-                    return new ReadOnlyCollection<Rect>(new List<Rect>(0));
+                    return ReadOnlyCollection<Rect>.Empty;
                 }
             }
 

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/DocumentViewer.cs

@@ -1231,7 +1231,7 @@ protected override ReadOnlyCollection<DocumentPageView> GetPageViewsCollection(o
             else
             {
                 //Return an empty collection (null is not valid).
-                pageViews = new ReadOnlyCollection<DocumentPageView>(new List<DocumentPageView>(0));
+                pageViews = ReadOnlyCollection<DocumentPageView>.Empty;
             }
 
             return pageViews;

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/Primitives/DocumentViewerBase.cs

@@ -70,7 +70,7 @@ static DocumentViewerBase()
         protected DocumentViewerBase()
             : base()
         {
-            _pageViews = new ReadOnlyCollection<DocumentPageView>(new List<DocumentPageView>());
+            _pageViews = ReadOnlyCollection<DocumentPageView>.Empty;
             // By default text selection is enabled.
             SetFlags(true, Flags.IsSelectionEnabled);
         }

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/TextChangedEventArgs.cs

@@ -86,7 +86,7 @@ public TextChangedEventArgs(RoutedEvent id, UndoAction action, ICollection<TextC
         /// <param name="id">event id</param>
         /// <param name="action">UndoAction</param>
         public TextChangedEventArgs(RoutedEvent id, UndoAction action)
-            : this(id, action, new ReadOnlyCollection<TextChange>(new List<TextChange>()))
+            : this(id, action, ReadOnlyCollection<TextChange>.Empty)
         {
         }
 

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/TextFlow.cs

@@ -989,7 +989,7 @@ protected virtual ReadOnlyCollection<Rect> GetRectanglesCore(ContentElement chil
                 throw new ArgumentNullException("child");
             }
 
-            ReadOnlyCollection<Rect> rectangles = new ReadOnlyCollection<Rect>(new List<Rect>(0));
+            ReadOnlyCollection<Rect> rectangles = ReadOnlyCollection<Rect>.Empty;
             if (IsLayoutDataValid)
             {
                 // Here we must call the internal function on document page that tells it whether or not
@@ -1019,7 +1019,7 @@ protected virtual IEnumerator<IInputElement> HostedElementsCore
                 else
                 {
                     // Return empty collection
-                    hostedElements = new HostedElements(new ReadOnlyCollection<TextSegment>(new List<TextSegment>(0)));
+                    hostedElements = new HostedElements(ReadOnlyCollection<TextSegment>.Empty);
                 }
                 return hostedElements;
             }

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Schema/MemberReflector.cs

@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Reflection;
 using System.Windows.Markup;
@@ -91,7 +92,7 @@ internal static MemberReflector UnknownReflector
                     s_UnknownReflector._typeConverter.Value = null;
                     s_UnknownReflector._valueSerializer.Value = null;
 
-                    s_UnknownReflector.DependsOn = XamlType.EmptyList<XamlMember>.Value;
+                    s_UnknownReflector.DependsOn = ReadOnlyCollection<XamlMember>.Empty;
                     s_UnknownReflector.Invoker = XamlMemberInvoker.UnknownInvoker;
                     s_UnknownReflector.Type = XamlLanguage.Object;
                 }

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlMember.cs

@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Reflection;
 using System.Threading;
@@ -346,7 +347,7 @@ public IList<XamlMember> DependsOn
                 EnsureReflector();
                 if (_reflector.DependsOn is null)
                 {
-                    _reflector.DependsOn = LookupDependsOn() ?? XamlType.EmptyList<XamlMember>.Value;
+                    _reflector.DependsOn = LookupDependsOn() ?? ReadOnlyCollection<XamlMember>.Empty;
                 }
                 return _reflector.DependsOn;
             }

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlType.cs

@@ -233,7 +233,7 @@ public IList<XamlType> AllowedContentTypes
                 if (_reflector.AllowedContentTypes is null)
                 {
                     _reflector.AllowedContentTypes = LookupAllowedContentTypes() ??
-                        EmptyList<XamlType>.Value;
+                        ReadOnlyCollection<XamlType>.Empty;
                 }
                 return _reflector.AllowedContentTypes;
             }
@@ -251,7 +251,7 @@ public IList<XamlType> ContentWrappers
                 if (_reflector.ContentWrappers is null)
                 {
                     _reflector.ContentWrappers = LookupContentWrappers() ??
-                        EmptyList<XamlType>.Value;
+                        ReadOnlyCollection<XamlType>.Empty;
                 }
                 return _reflector.ContentWrappers;
             }
@@ -598,7 +598,7 @@ internal ICollection<XamlMember> GetAllExcludedReadOnlyMembers()
             EnsureReflector();
             if (_reflector.ExcludedReadOnlyMembers is null)
             {
-                _reflector.ExcludedReadOnlyMembers = LookupAllExcludedReadOnlyMembers() ?? EmptyList<XamlMember>.Value;
+                _reflector.ExcludedReadOnlyMembers = LookupAllExcludedReadOnlyMembers() ?? ReadOnlyCollection<XamlMember>.Empty;
             }
             return _reflector.ExcludedReadOnlyMembers;
         }
@@ -609,7 +609,7 @@ internal IEnumerable<ConstructorInfo> GetConstructors()
         {
             if (UnderlyingType is null)
             {
-                return EmptyList<ConstructorInfo>.Value;
+                return ReadOnlyCollection<ConstructorInfo>.Empty;
             }
             if (IsPublic)
             {
@@ -680,7 +680,7 @@ protected virtual XamlMember LookupAliasedProperty(XamlDirective directive)
 
         protected virtual IList<XamlType> LookupAllowedContentTypes()
         {
-            IList<XamlType> contentWrappers = ContentWrappers ?? EmptyList<XamlType>.Value;
+            IList<XamlType> contentWrappers = ContentWrappers ?? ReadOnlyCollection<XamlType>.Empty;
             List<XamlType> result = new List<XamlType>(contentWrappers.Count + 1);
             result.Add(ItemType);
 
@@ -1461,7 +1461,7 @@ internal static ReadOnlyCollection<T> GetReadOnly<T>(IList<T> list)
             {
                 return new ReadOnlyCollection<T>(list);
             }
-            return EmptyList<T>.Value;
+            return ReadOnlyCollection<T>.Empty;
         }
 
         private static ReadOnlyCollection<XamlType> GetTypeArguments(IList<XamlType> typeArguments)
@@ -1823,11 +1823,5 @@ private static bool TypeArgumentsAreEqual(XamlType xamlType1, XamlType xamlType2
         }
 
         #endregion
-
-        internal static class EmptyList<T>
-        {
-            public static readonly ReadOnlyCollection<T> Value =
-                new ReadOnlyCollection<T>(Array.Empty<T>());
-        }
     }
 }