From b4856dd58c39c45a00cf63ca1a3841664ed1f2cb Mon Sep 17 00:00:00 2001
From: Ilya <darpa@yandex.ru>
Date: Fri, 4 Jun 2021 09:05:44 +0500
Subject: [PATCH] Thread-safe HttpKnownHeaderNames initialization

---
 .../WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs | 40 +++++++++----------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs
index 80d07a54ddf..0acd7c33567 100644
--- a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs
+++ b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs
@@ -78,31 +78,29 @@ internal static class HttpKnownHeaderNames
 
         #endregion Known_HTTP_Header_Names
 
-        private static HashSet<string> s_contentHeaderSet = null;
+        private static readonly HashSet<string> s_contentHeaderSet;
 
-        internal static HashSet<string> ContentHeaders
+        static HttpKnownHeaderNames()
         {
-            get
-            {
-                if (s_contentHeaderSet == null)
-                {
-                    s_contentHeaderSet = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            // Thread-safe initialization.
+            s_contentHeaderSet = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
 
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.Allow);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentDisposition);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentEncoding);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLanguage);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLength);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLocation);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentMD5);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentRange);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentType);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.Expires);
-                    s_contentHeaderSet.Add(HttpKnownHeaderNames.LastModified);
-                }
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.Allow);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentDisposition);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentEncoding);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLanguage);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLength);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentLocation);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentMD5);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentRange);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.ContentType);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.Expires);
+            s_contentHeaderSet.Add(HttpKnownHeaderNames.LastModified);
+        }
 
-                return s_contentHeaderSet;
-            }
+        internal static HashSet<string> ContentHeaders
+        {
+            get => s_contentHeaderSet;
         }
     }
 }