From 522854696fe2c1260d0563659154a40ddf829d54 Mon Sep 17 00:00:00 2001
From: Theodore Tsirpanis <12659251+teo-tsirpanis@users.noreply.github.com>
Date: Thu, 17 Sep 2020 18:58:21 +0300
Subject: [PATCH] Avoid race condition in WebClient.IsBusy. (#42076)

---
 src/libraries/System.Net.WebClient/src/System/Net/WebClient.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Net.WebClient/src/System/Net/WebClient.cs b/src/libraries/System.Net.WebClient/src/System/Net/WebClient.cs
index 8849777..c02b169 100644
--- a/src/libraries/System.Net.WebClient/src/System/Net/WebClient.cs
+++ b/src/libraries/System.Net.WebClient/src/System/Net/WebClient.cs
@@ -213,7 +213,7 @@ namespace System.Net
 
         public RequestCachePolicy? CachePolicy { get; set; }
 
-        public bool IsBusy => _asyncOp != null;
+        public bool IsBusy => Volatile.Read(ref _callNesting) > 0;
 
         protected virtual WebRequest GetWebRequest(Uri address)
         {
-- 
2.7.4