Use [ThreadStatic] in Gdip.ThreadData.

Author: teo-tsirpanis

src/libraries/System.Drawing.Common/src/System/Drawing/Gdiplus.cs

@@ -3,13 +3,9 @@
 
 using System.Collections;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Reflection;
-using System.Runtime.CompilerServices;
-using System.Runtime.ConstrainedExecution;
 using System.Runtime.InteropServices;
-using System.Threading;
 
 namespace System.Drawing
 {
@@ -19,7 +15,9 @@ internal static partial class SafeNativeMethods
         internal static partial class Gdip
         {
             private static readonly IntPtr s_initToken;
-            private const string ThreadDataSlotName = "system.drawing.threaddata";
+
+            [ThreadStatic]
+            private static IDictionary? t_threadData;
 
             static Gdip()
             {
@@ -47,21 +45,7 @@ static Gdip()
             /// a per-thread basis. This way we can avoid 'object in use' crashes when different threads are
             /// referencing the same drawing object.
             /// </summary>
-            internal static IDictionary ThreadData
-            {
-                get
-                {
-                    LocalDataStoreSlot slot = Thread.GetNamedDataSlot(ThreadDataSlotName);
-                    IDictionary? threadData = (IDictionary?)Thread.GetData(slot);
-                    if (threadData == null)
-                    {
-                        threadData = new Hashtable();
-                        Thread.SetData(slot, threadData);
-                    }
-
-                    return threadData;
-                }
-            }
+            internal static IDictionary ThreadData => t_threadData ??= new Hashtable();
 
             // Used to ensure static constructor has run.
             internal static void DummyFunction()