Cleanup uses of Interlocked.CompareExchange<object>

src/coreclr/System.Private.CoreLib/src/System/MulticastDelegate.CoreCLR.cs

@@ -144,7 +144,7 @@ private bool InvocationListEquals(MulticastDelegate d)
 
         private static bool TrySetSlot(object?[] a, int index, object o)
         {
-            if (a[index] == null && Threading.Interlocked.CompareExchange<object?>(ref a[index], o, null) == null)
+            if (a[index] == null && Threading.Interlocked.CompareExchange(ref a[index], o, null) == null)
                 return true;
 
             // The slot may be already set because we have added and removed the same method before.

src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs

@@ -34,7 +34,7 @@ internal sealed partial class RuntimeAssembly : Assembly
 
         #endregion
 
-        internal IntPtr GetUnderlyingNativeHandle() { return m_assembly; }
+        internal IntPtr GetUnderlyingNativeHandle() =>  m_assembly;
 
         private sealed class ManifestResourceStream : UnmanagedMemoryStream
         {
@@ -52,17 +52,8 @@ internal unsafe ManifestResourceStream(RuntimeAssembly manifestAssembly, byte* p
             // NOTE: no reason to override Write(Span<byte>), since a ManifestResourceStream is read-only.
         }
 
-        internal object SyncRoot
-        {
-            get
-            {
-                if (m_syncRoot == null)
-                {
-                    Interlocked.CompareExchange<object?>(ref m_syncRoot, new object(), null);
-                }
-                return m_syncRoot;
-            }
-        }
+        internal object SyncRoot =>
+            m_syncRoot ?? Interlocked.CompareExchange(ref m_syncRoot, new object(), null) ?? m_syncRoot;
 
         public override event ModuleResolveEventHandler? ModuleResolve
         {

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableDictionary_2.Builder.cs

@@ -56,11 +56,6 @@
             /// </summary>
             private int _version;
 
-            /// <summary>
-            /// The object callers may use to synchronize access to this collection.
-            /// </summary>
-            private object? _syncRoot;
-
             /// <summary>
             /// Initializes a new instance of the <see cref="ImmutableDictionary{TKey, TValue}.Builder"/> class.
             /// </summary>
@@ -251,18 +246,8 @@
             /// </summary>
             /// <returns>An object that can be used to synchronize access to the <see cref="ICollection"/>.</returns>
             [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-            object ICollection.SyncRoot
-            {
-                get
-                {
-                    if (_syncRoot == null)
-                    {
-                        Threading.Interlocked.CompareExchange<object?>(ref _syncRoot, new object(), null);
-                    }
-
-                    return _syncRoot;
-                }
-            }
+            object ICollection.SyncRoot =>
+                 field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
             /// <summary>
             /// Gets a value indicating whether access to the <see cref="ICollection"/> is synchronized (thread safe).

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Builder.cs

@@ -46,11 +46,6 @@
             /// </summary>
             private int _version;
 
-            /// <summary>
-            /// The object callers may use to synchronize access to this collection.
-            /// </summary>
-            private object? _syncRoot;
-
             /// <summary>
             /// Initializes a new instance of the <see cref="Builder"/> class.
             /// </summary>
@@ -1159,18 +1154,8 @@
             /// </summary>
             /// <returns>An object that can be used to synchronize access to the <see cref="ICollection"/>.</returns>
             [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-            object ICollection.SyncRoot
-            {
-                get
-                {
-                    if (_syncRoot == null)
-                    {
-                        System.Threading.Interlocked.CompareExchange<object?>(ref _syncRoot, new object(), null);
-                    }
-
-                    return _syncRoot;
-                }
-            }
+            object ICollection.SyncRoot =>
+                 field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
             #endregion
         }
     }

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedDictionary_2.Builder.cs

@@ -59,11 +59,6 @@
             /// </summary>
             private int _version;
 
-            /// <summary>
-            /// The object callers may use to synchronize access to this collection.
-            /// </summary>
-            private object? _syncRoot;
-
             /// <summary>
             /// Initializes a new instance of the <see cref="Builder"/> class.
             /// </summary>
@@ -262,18 +257,8 @@
             /// </summary>
             /// <returns>An object that can be used to synchronize access to the <see cref="ICollection"/>.</returns>
             [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-            object ICollection.SyncRoot
-            {
-                get
-                {
-                    if (_syncRoot == null)
-                    {
-                        Threading.Interlocked.CompareExchange<object?>(ref _syncRoot, new object(), null);
-                    }
-
-                    return _syncRoot;
-                }
-            }
+            object ICollection.SyncRoot =>
+                 field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
             /// <summary>
             /// Gets a value indicating whether access to the <see cref="ICollection"/> is synchronized (thread safe).

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet_1.Builder.cs

@@ -51,11 +51,6 @@
             /// </summary>
             private int _version;
 
-            /// <summary>
-            /// The object callers may use to synchronize access to this collection.
-            /// </summary>
-            private object? _syncRoot;
-
             /// <summary>
             /// Initializes a new instance of the <see cref="Builder"/> class.
             /// </summary>
@@ -505,18 +500,8 @@
             /// </summary>
             /// <returns>An object that can be used to synchronize access to the <see cref="ICollection"/>.</returns>
             [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-            object ICollection.SyncRoot
-            {
-                get
-                {
-                    if (_syncRoot == null)
-                    {
-                        Threading.Interlocked.CompareExchange<object?>(ref _syncRoot, new object(), null);
-                    }
-
-                    return _syncRoot;
-                }
-            }
+            object ICollection.SyncRoot =>
+                 field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
             #endregion
         }
     }

src/libraries/System.Diagnostics.TraceSource/src/System/Diagnostics/Switch.cs

@@ -25,25 +25,14 @@ public abstract class Switch
         private bool _initializing;
         private volatile string? _switchValueString = string.Empty;
         private readonly string _defaultValue;
-        private object? _initializedLock;
 
         private static readonly List<WeakReference<Switch>> s_switches = new List<WeakReference<Switch>>();
         private static int s_LastCollectionCount;
         private StringDictionary? _attributes;
 
-        private object InitializedLock
-        {
-            get
-            {
-                if (_initializedLock == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref _initializedLock, o, null);
-                }
+        private object InitializedLock =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
-                return _initializedLock;
-            }
-        }
 
         /// <devdoc>
         /// <para>Initializes a new instance of the <see cref='System.Diagnostics.Switch'/>

src/libraries/System.Private.CoreLib/src/System/TimeZone.cs

@@ -15,19 +15,8 @@ public abstract class TimeZone
         private static volatile TimeZone? currentTimeZone;
 
         // Private object for locking instead of locking on a public type for SQL reliability work.
-        private static object? s_InternalSyncObject;
-        private static object InternalSyncObject
-        {
-            get
-            {
-                if (s_InternalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
-                }
-                return s_InternalSyncObject;
-            }
-        }
+        private static object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         protected TimeZone()
         {

src/libraries/System.Private.Xml.Linq/src/System/Xml/Linq/XContainer.cs

@@ -75,7 +75,7 @@ public XNode? LastNode
                     XText t = new XText(s);
                     t.parent = this;
                     t.next = t;
-                    Interlocked.CompareExchange<object>(ref content, t, s);
+                    Interlocked.CompareExchange(ref content, t, s);
                 }
                 return (XNode)content;
             }

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaSet.cs

@@ -56,20 +56,8 @@ public class XmlSchemaSet
         private XmlSchemaObjectTable? _typeExtensions;
 
         //Thread safety
-        private object? _internalSyncObject;
-        internal object InternalSyncObject
-        {
-            get
-            {
-                if (_internalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref _internalSyncObject, o, null);
-                }
-
-                return _internalSyncObject;
-            }
-        }
+        internal object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         //Constructors
 

src/libraries/System.Text.Encoding.CodePages/src/System/Text/DBCSCodePageEncoding.cs

@@ -225,19 +225,8 @@ protected virtual unsafe void CleanUpEndBytes(char* chars)
         }
 
         // Private object for locking instead of locking on a public type for SQL reliability work.
-        private static object? s_InternalSyncObject;
-        private static object InternalSyncObject
-        {
-            get
-            {
-                if (s_InternalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
-                }
-                return s_InternalSyncObject;
-            }
-        }
+        private static object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         // Read in our best fit table
         protected override unsafe void ReadBestFitTable()

src/libraries/System.Text.Encoding.CodePages/src/System/Text/DecoderBestFitFallback.cs

@@ -47,19 +47,8 @@ internal sealed class InternalDecoderBestFitFallbackBuffer : DecoderFallbackBuff
         private readonly InternalDecoderBestFitFallback _oFallback;
 
         // Private object for locking instead of locking on a public type for SQL reliability work.
-        private static object? s_InternalSyncObject;
-        private static object InternalSyncObject
-        {
-            get
-            {
-                if (s_InternalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
-                }
-                return s_InternalSyncObject;
-            }
-        }
+        private static object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         // Constructor
         public InternalDecoderBestFitFallbackBuffer(InternalDecoderBestFitFallback fallback)

src/libraries/System.Text.Encoding.CodePages/src/System/Text/EncoderBestFitFallback.cs

@@ -47,19 +47,8 @@ internal sealed class InternalEncoderBestFitFallbackBuffer : EncoderFallbackBuff
         private int _iSize;
 
         // Private object for locking instead of locking on a public type for SQL reliability work.
-        private static object? s_InternalSyncObject;
-        private static object InternalSyncObject
-        {
-            get
-            {
-                if (s_InternalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
-                }
-                return s_InternalSyncObject;
-            }
-        }
+        private static object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         // Constructor
         public InternalEncoderBestFitFallbackBuffer(InternalEncoderBestFitFallback fallback)

src/libraries/System.Text.Encoding.CodePages/src/System/Text/SBCSCodePageEncoding.cs

@@ -129,19 +129,8 @@ protected override unsafe void LoadManagedCodePage()
         }
 
         // Private object for locking instead of locking on a public type for SQL reliability work.
-        private static object? s_InternalSyncObject;
-        private static object InternalSyncObject
-        {
-            get
-            {
-                if (s_InternalSyncObject == null)
-                {
-                    object o = new object();
-                    Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
-                }
-                return s_InternalSyncObject;
-            }
-        }
+        private static object InternalSyncObject =>
+            field ?? Interlocked.CompareExchange(ref field, new object(), null) ?? field;
 
         // Read in our best fit table
         protected override unsafe void ReadBestFitTable()