Merge pull request dotnet#20963 from lmolkova/ActivityNoCrossAppDomain

Store Activity wrapped into ObjectHandle in Logical CallContext

src/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.Current.net45.cs

@@ -2,13 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Runtime.Remoting;
 using System.Runtime.Remoting.Messaging;
 using System.Security;
 
 namespace System.Diagnostics
 {
-    // this code is specific to .NET 4.5 and uses CallContext to store Activity.Current which requires Activity to be Serializable.
-    [Serializable] // DO NOT remove
     public partial class Activity
     {
         /// <summary>
@@ -22,26 +21,38 @@ public static Activity Current
 #endif
             get
             {
-                return (Activity)CallContext.LogicalGetData(FieldKey);
+                ObjectHandle activityHandle = (ObjectHandle)CallContext.LogicalGetData(FieldKey);
+
+                // Unwrap the Activity if it was set in the same AppDomain (as FieldKey is AppDomain-specific). 
+                if (activityHandle != null)
+                {
+                    return (Activity)activityHandle.Unwrap();
+                }
+                return null;
             }
 
 #if ALLOW_PARTIALLY_TRUSTED_CALLERS
             [System.Security.SecuritySafeCriticalAttribute]
 #endif
             private set
             {
-                CallContext.LogicalSetData(FieldKey, value);
+                // Applications may implicitly or explicitly call other AppDomains
+                // that do not have DiagnosticSource DLL, therefore may not be able to resolve Activity type stored in the logical call context. 
+                // To avoid it, we wrap Activity with ObjectHandle.
+                CallContext.LogicalSetData(FieldKey, new ObjectHandle(value));
             }
         }
 
 #region private
 
-        [Serializable] // DO NOT remove
         private partial class KeyValueListNode
         {
         }
 
-        private static readonly string FieldKey = $"{typeof(Activity).FullName}";
+        // Slot name depends on the AppDomain Id in order to prevent AppDomains to use the same Activity
+        // Cross AppDomain calls are considered as 'external' i.e. only Activity Id and Baggage should be propagated and 
+        // new Activity should be started for the RPC calls (incoming and outgoing) 
+        private static readonly string FieldKey = $"{typeof(Activity).FullName}_{AppDomain.CurrentDomain.Id}";
 #endregion
     }
 }