Introduce public setter for Activity

src/System.Diagnostics.DiagnosticSource/ref/System.Diagnostics.DiagnosticSourceActivity.cs

@@ -34,7 +34,7 @@ public static Activity Current
 #if ALLOW_PARTIALLY_TRUSTED_CALLERS
        [System.Security.SecuritySafeCriticalAttribute]
 #endif
-        private set {}
+        set {}
     }
   }
   public abstract partial class DiagnosticSource {

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

@@ -11,7 +11,7 @@ namespace System.Diagnostics
     public partial class Activity
     {
         /// <summary>
-        /// Returns the current operation (Activity) for the current thread.  This flows 
+        /// Gets or sets the current operation (Activity) for the current thread.  This flows 
         /// across async calls.
         /// </summary>
         public static Activity Current
@@ -22,37 +22,44 @@ public static Activity Current
             get
             {
                 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
+            set
             {
-                // 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));
+                if (ValidateSetCurrent)
+                {
+                    SetCurrent(value);
+                }
             }
         }
 
 #region private
 
-        private partial class KeyValueListNode
+#if ALLOW_PARTIALLY_TRUSTED_CALLERS
+        [System.Security.SecuritySafeCriticalAttribute]
+#endif
+        private static void SetCurrent(Activity activity)
         {
+            // 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(activity));
         }
 
         // 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
+#endregion //private
     }
-}
+}

src/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.Current.net46.cs

@@ -9,17 +9,28 @@ namespace System.Diagnostics
     public partial class Activity
     {
         /// <summary>
-        /// Returns the current operation (Activity) for the current thread.  This flows 
+        /// Gets or sets the current operation (Activity) for the current thread.  This flows 
         /// across async calls.
         /// </summary>
         public static Activity Current
         {
             get { return s_current.Value; }
-            private set { s_current.Value = value; }
+            set
+            {
+                if (ValidateSetCurrent(value))
+                {
+                    SetCurrent(value);
+                }
+            }
         }
 
 #region private
+        private static void SetCurrent(Activity activity)
+        {
+            s_current.Value = activity;
+        }
+
         private static readonly AsyncLocal<Activity> s_current = new AsyncLocal<Activity>();
 #endregion // private
     }
-}
+}

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

@@ -3,7 +3,9 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
-using System.Security;
+#if ALLOW_PARTIALLY_TRUSTED_CALLERS
+    using System.Security;
+#endif
 using System.Threading;
 
 namespace System.Diagnostics
@@ -308,7 +310,7 @@ public Activity Start()
                 }
 
                 Id = GenerateId();
-                Current = this;
+                SetCurrent(this);
             }
             return this;
         }
@@ -337,7 +339,7 @@ public void Stop()
                     SetEndTime(GetUtcNow());
                 }
 
-                Current = Parent;
+                SetCurrent(Parent);
             }
         }
 
@@ -446,6 +448,17 @@ private static unsafe long GetRandomNumber()
             return *((long*)&g);
         }
 
+        private static bool ValidateSetCurrent(Activity activity)
+        {
+            bool canSet = activity == null || (activity.Id != null && !activity.isFinished);
+            if (!canSet)
+            {
+                NotifyError(new InvalidOperationException("Trying to set an Activity that is not running"));
+            }
+
+            return canSet;
+        }
+
         private string _rootId;
         private int _currentChildId;  // A unique number for all children of this activity.  
 

src/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -532,6 +532,62 @@ public async Task ActivityCurrentFlowsWithAsyncComplex()
             Assert.Same(originalActivity, Activity.Current);
         }
 
+        /// <summary>
+        /// Tests that Activity.Current could be set
+        /// </summary>
+        [Fact]
+        public async Task ActivityCurrentSet()
+        {
+            Activity activity = new Activity("activity");
+
+            // start Activity in the 'child' context
+            await Task.Run(() => activity.Start());
+
+            Assert.Null(Activity.Current);
+            Activity.Current = activity;
+            Assert.Same(activity, Activity.Current);
+        }
+
+        /// <summary>
+        /// Tests that Activity.Current could be set to null
+        /// </summary>
+        [Fact]
+        public void ActivityCurrentSetToNull()
+        {
+            Activity started = new Activity("started").Start();
+
+            Activity.Current = null;
+            Assert.Null(Activity.Current);
+        }
+
+        /// <summary>
+        /// Tests that Activity.Current could not be set to Activity
+        /// that has not been started yet
+        /// </summary>
+        [Fact]
+        public void ActivityCurrentNotSetToNotStarted()
+        {
+            Activity started = new Activity("started").Start();
+            Activity notStarted = new Activity("notStarted");
+
+            Activity.Current = notStarted;
+            Assert.Same(started, Activity.Current);
+        }
+
+        /// <summary>
+        /// Tests that Activity.Current could not be set to stopped Activity
+        /// </summary>
+        [Fact]
+        public void ActivityCurrentNotSetToStopped()
+        {
+            Activity started = new Activity("started").Start();
+            Activity stopped = new Activity("stopped").Start();
+            stopped.Stop();
+
+            Activity.Current = stopped;
+            Assert.Same(started, Activity.Current);
+        }
+
         private class TestObserver : IObserver<KeyValuePair<string, object>>
         {
             public string EventName { get; private set; }

src/System.Diagnostics.DiagnosticSource/tests/System.Diagnostics.DiagnosticSource.Tests.csproj

@@ -36,5 +36,8 @@
       <Link>Common\System\Net\Configuration.Http.cs</Link>
     </Compile>
   </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
 </Project>