From e803a1b89dd1c831d37969298ca6e4c173623195 Mon Sep 17 00:00:00 2001
From: Eric Erhardt <eric.erhardt@microsoft.com>
Date: Tue, 23 Feb 2021 15:09:58 -0600
Subject: [PATCH] Build Threading.Tasks.DataFlow and ComponentModel.Annotations
 for NetCoreAppCurrent

Fix #48662
---
 .../src/System.ComponentModel.Annotations.csproj | 15 ++++++++++++++-
 .../src/Base/DataflowBlock.cs                    | 14 +++++++-------
 .../src/Blocks/BatchBlock.cs                     |  6 +++---
 .../src/Blocks/BatchedJoinBlock.cs               | 10 +++++-----
 .../src/Blocks/BroadcastBlock.cs                 | 16 ++++++++--------
 .../src/Blocks/BufferBlock.cs                    |  4 ++--
 .../src/Blocks/JoinBlock.cs                      | 14 +++++++-------
 .../src/Blocks/TransformBlock.cs                 |  4 ++--
 .../src/Blocks/WriteOnceBlock.cs                 |  4 ++--
 .../src/Internal/ProducerConsumerQueues.cs       |  7 +++----
 .../src/Internal/SourceCore.cs                   | 14 +++++++-------
 .../src/Internal/SpscTargetCore.cs               |  8 ++++----
 .../src/Internal/TargetCore.cs                   |  4 ++--
 .../src/System.Threading.Tasks.Dataflow.csproj   | 14 ++++++++++++--
 14 files changed, 78 insertions(+), 56 deletions(-)

diff --git a/src/libraries/System.ComponentModel.Annotations/src/System.ComponentModel.Annotations.csproj b/src/libraries/System.ComponentModel.Annotations/src/System.ComponentModel.Annotations.csproj
index bf49fb5827b08..6291ade5c7046 100644
--- a/src/libraries/System.ComponentModel.Annotations/src/System.ComponentModel.Annotations.csproj
+++ b/src/libraries/System.ComponentModel.Annotations/src/System.ComponentModel.Annotations.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.1</TargetFrameworks>
+    <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
     <Nullable>enable</Nullable>
     <!--
       Since many resource strings in this library are shown to an end-user,
@@ -59,4 +60,16 @@
     <Compile Include="$(CommonPath)System\NotImplemented.cs"
              Link="Common\System\NotImplemented.cs" />
   </ItemGroup>
+  <ItemGroup Condition="$([MSBuild]::GetTargetFrameworkIdentifier('$(TargetFramework)')) == '.NETCoreApp'">
+    <Reference Include="System.Collections" />
+    <Reference Include="System.Collections.Concurrent" />
+    <Reference Include="System.ComponentModel" />
+    <Reference Include="System.ComponentModel.Primitives" />
+    <Reference Include="System.ComponentModel.TypeConverter" />
+    <Reference Include="System.Linq" />
+    <Reference Include="System.Runtime" />
+    <Reference Include="System.Resources.ResourceManager" />
+    <Reference Include="System.Text.RegularExpressions" />
+    <Reference Include="System.Threading" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Base/DataflowBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Base/DataflowBlock.cs
index 2785f3ea4d4ab..e3393d1c474c4 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Base/DataflowBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Base/DataflowBlock.cs
@@ -133,7 +133,7 @@ private bool RunPredicate(T item)
 
             /// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Targets/Member[@name="OfferMessage"]/*' />
 #pragma warning disable 8617
-            DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader messageHeader, T messageValue, ISourceBlock<T> source, bool consumeToAccept)
+            DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader messageHeader, T messageValue, ISourceBlock<T>? source, bool consumeToAccept)
 #pragma warning restore 8617
             {
                 // Validate arguments.  Some targets may have a null source, but FilteredLinkPropagator
@@ -939,7 +939,7 @@ public static TOutput Receive<TOutput>(
 
             // Do fast path checks for both cancellation and data already existing.
             cancellationToken.ThrowIfCancellationRequested();
-            TOutput fastCheckedItem;
+            TOutput? fastCheckedItem;
             var receivableSource = source as IReceivableSourceBlock<TOutput>;
             if (receivableSource != null && receivableSource.TryReceive(null, out fastCheckedItem))
             {
@@ -995,7 +995,7 @@ private static Task<TOutput> ReceiveCore<TOutput>(
                 {
                     try
                     {
-                        TOutput fastCheckedItem;
+                        TOutput? fastCheckedItem;
                         if (receivableSource.TryReceive(null, out fastCheckedItem))
                         {
                             return Task.FromResult<TOutput>(fastCheckedItem);
@@ -1091,7 +1091,7 @@ private static Task<TOutput> ReceiveCoreByLinking<TOutput>(ISourceBlock<TOutput>
                 // So we are racing to dispose of the unlinker.
                 if (Volatile.Read(ref target._cleanupReserved))
                 {
-                    IDisposable disposableUnlink = Interlocked.CompareExchange(ref target._unlink, null, unlink);
+                    IDisposable? disposableUnlink = Interlocked.CompareExchange<IDisposable?>(ref target._unlink, null, unlink);
                     if (disposableUnlink != null) disposableUnlink.Dispose();
                 }
             }
@@ -1173,7 +1173,7 @@ DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader message
                     {
                         // Accept the message if possible and complete this task with the message's value.
                         bool consumed = true;
-                        T acceptedValue = consumeToAccept ? source!.ConsumeMessage(messageHeader, this, out consumed) : messageValue;
+                        T? acceptedValue = consumeToAccept ? source!.ConsumeMessage(messageHeader, this, out consumed) : messageValue;
                         if (consumed)
                         {
                             status = DataflowMessageStatus.Accepted;
@@ -1962,7 +1962,7 @@ private static bool TryChooseFromSource<T>(
             Debug.Assert(scheduler != null, "Expected a non-null scheduler");
 
             // Try to receive from the source.  If we can't, bail.
-            T result;
+            T? result;
             var receivableSource = source as IReceivableSourceBlock<T>;
             if (receivableSource == null || !receivableSource.TryReceive(out result))
             {
@@ -2198,7 +2198,7 @@ public DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader, T
                     if (consumeToAccept)
                     {
                         bool consumed;
-                        messageValue = source!.ConsumeMessage(messageHeader, this, out consumed);
+                        messageValue = source!.ConsumeMessage(messageHeader, this, out consumed)!;
                         if (!consumed) return DataflowMessageStatus.NotAvailable;
                     }
 
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchBlock.cs
index af2775e9031f9..92a271d0db4f7 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchBlock.cs
@@ -387,7 +387,7 @@ internal DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader,
                             Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                             bool consumed;
-                            messageValue = source.ConsumeMessage(messageHeader, _owningBatch, out consumed);
+                            messageValue = source.ConsumeMessage(messageHeader, _owningBatch, out consumed)!;
                             if (!consumed) return DataflowMessageStatus.NotAvailable;
                         }
 
@@ -1004,7 +1004,7 @@ private void ConsumeReservedMessagesNonGreedy()
                     KeyValuePair<ISourceBlock<T>, KeyValuePair<DataflowMessageHeader, T>> sourceAndMessage = reserved[i];
                     reserved[i] = default(KeyValuePair<ISourceBlock<T>, KeyValuePair<DataflowMessageHeader, T>>); // in case of exception from ConsumeMessage
                     bool consumed;
-                    T consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value.Key, _owningBatch, out consumed);
+                    T? consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value.Key, _owningBatch, out consumed);
                     if (!consumed)
                     {
                         // The protocol broke down, so throw an exception, as this is fatal.  Before doing so, though,
@@ -1056,7 +1056,7 @@ private void ConsumeReservedMessagesGreedyBounded()
                     KeyValuePair<ISourceBlock<T>, KeyValuePair<DataflowMessageHeader, T>> sourceAndMessage = reserved[i];
                     reserved[i] = default(KeyValuePair<ISourceBlock<T>, KeyValuePair<DataflowMessageHeader, T>>); // in case of exception from ConsumeMessage
                     bool consumed;
-                    T consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value.Key, _owningBatch, out consumed);
+                    T? consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value.Key, _owningBatch, out consumed);
                     if (consumed)
                     {
                         var consumedMessage = new KeyValuePair<DataflowMessageHeader, T>(sourceAndMessage.Value.Key, consumedValue!);
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchedJoinBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchedJoinBlock.cs
index 8099f49cae70c..0ddbf1c216979 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchedJoinBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BatchedJoinBlock.cs
@@ -72,9 +72,9 @@ public BatchedJoinBlock(int batchSize, GroupingDataflowBlockOptions dataflowBloc
             // messages, and thus when there may be a few stragglers we need to make a batch out of.
             Action createBatchAction = () =>
             {
-                if (_target1.Count > 0 || _target2.Count > 0)
+                if (_target1!.Count > 0 || _target2!.Count > 0)
                 {
-                    _source.AddMessage(Tuple.Create(_target1.GetAndEmptyMessages(), _target2.GetAndEmptyMessages()));
+                    _source.AddMessage(Tuple.Create(_target1.GetAndEmptyMessages(), _target2!.GetAndEmptyMessages()));
                 }
             };
 
@@ -329,9 +329,9 @@ public BatchedJoinBlock(int batchSize, GroupingDataflowBlockOptions dataflowBloc
             // messages, and thus when there may be a few stragglers we need to make a batch out of.
             Action createBatchAction = () =>
             {
-                if (_target1.Count > 0 || _target2.Count > 0 || _target3.Count > 0)
+                if (_target1!.Count > 0 || _target2!.Count > 0 || _target3!.Count > 0)
                 {
-                    _source.AddMessage(Tuple.Create(_target1.GetAndEmptyMessages(), _target2.GetAndEmptyMessages(), _target3.GetAndEmptyMessages()));
+                    _source.AddMessage(Tuple.Create(_target1.GetAndEmptyMessages(), _target2!.GetAndEmptyMessages(), _target3!.GetAndEmptyMessages()));
                 }
             };
 
@@ -598,7 +598,7 @@ public DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader, T
                     Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                     bool consumed;
-                    messageValue = source.ConsumeMessage(messageHeader, this, out consumed);
+                    messageValue = source.ConsumeMessage(messageHeader, this, out consumed)!;
                     if (!consumed) return DataflowMessageStatus.NotAvailable;
                 }
                 _messages.Add(messageValue!);
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BroadcastBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BroadcastBlock.cs
index 9f9b93298f86c..b7a76c2bd2289 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BroadcastBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BroadcastBlock.cs
@@ -191,7 +191,7 @@ DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader message
                         Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                         bool consumed;
-                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed);
+                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed)!;
                         if (!consumed) return DataflowMessageStatus.NotAvailable;
                     }
 
@@ -352,7 +352,7 @@ private bool ConsumeAndStoreOneMessageIfAvailable()
                 bool consumed = false;
                 try
                 {
-                    T consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value, this, out consumed);
+                    T? consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value, this, out consumed);
                     if (consumed)
                     {
                         _source.AddMessage(consumedValue!);
@@ -577,7 +577,7 @@ internal bool TryReceive(Predicate<TOutput>? filter, [MaybeNullWhen(false)] out
                 // synchronizing with other activities on the block.
                 // We don't want to execute the user-provided cloning delegate
                 // while holding the lock.
-                TOutput message;
+                TOutput? message;
                 bool isValid;
                 lock (OutgoingLock)
                 {
@@ -607,7 +607,7 @@ internal bool TryReceiveAll([NotNullWhen(true)] out IList<TOutput>? items)
             {
                 // Try to receive the one item this block may have.
                 // If we can, give back an array of one item. Otherwise, give back null.
-                TOutput item;
+                TOutput? item;
                 if (TryReceive(null, out item))
                 {
                     items = new TOutput[] { item };
@@ -683,7 +683,7 @@ private void OfferCurrentMessageToNewTarget(ITargetBlock<TOutput> target)
                 Common.ContractAssertMonitorStatus(ValueLock, held: false);
 
                 // Get the current message if there is one
-                TOutput currentMessage;
+                TOutput? currentMessage;
                 bool isValid;
                 lock (ValueLock)
                 {
@@ -725,7 +725,7 @@ private bool OfferToTargets()
                 Common.ContractAssertMonitorStatus(ValueLock, held: false);
 
                 DataflowMessageHeader header = default(DataflowMessageHeader);
-                TOutput message = default(TOutput);
+                TOutput? message = default(TOutput);
                 int numDequeuedMessages = 0;
                 lock (ValueLock)
                 {
@@ -1053,7 +1053,7 @@ internal IDisposable LinkTo(ITargetBlock<TOutput> target, DataflowLinkOptions li
                 if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, nameof(messageHeader));
                 if (target == null) throw new ArgumentNullException(nameof(target));
 
-                TOutput valueToClone;
+                TOutput? valueToClone;
                 lock (OutgoingLock) // We may currently be calling out under this lock to the target; requires it to be reentrant
                 {
                     lock (ValueLock)
@@ -1125,7 +1125,7 @@ internal void ReleaseReservation(DataflowMessageHeader messageHeader, ITargetBlo
                     // If someone else holds the reservation, bail.
                     if (_nextMessageReservedFor != target) throw new InvalidOperationException(SR.InvalidOperation_MessageNotReservedByTarget);
 
-                    TOutput messageToReoffer;
+                    TOutput? messageToReoffer;
                     lock (ValueLock)
                     {
                         // If this is not the message at the head of the queue, bail
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BufferBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BufferBlock.cs
index 6d5e702bb7f04..40bea6b0197b2 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BufferBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/BufferBlock.cs
@@ -118,7 +118,7 @@ DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader message
                         Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                         bool consumed;
-                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed);
+                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed)!;
                         if (!consumed) return DataflowMessageStatus.NotAvailable;
                     }
 
@@ -354,7 +354,7 @@ private bool ConsumeAndStoreOneMessageIfAvailable()
                 bool consumed = false;
                 try
                 {
-                    T consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value, this, out consumed);
+                    T? consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value, this, out consumed);
                     if (consumed)
                     {
                         _source.AddMessage(consumedValue!);
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/JoinBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/JoinBlock.cs
index 042c7adec71b8..7b5872023a02d 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/JoinBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/JoinBlock.cs
@@ -69,11 +69,11 @@ public JoinBlock(GroupingDataflowBlockOptions dataflowBlockOptions)
             _sharedResources = new JoinBlockTargetSharedResources(this, targets,
                 () =>
                 {
-                    _source.AddMessage(Tuple.Create(_target1.GetOneMessage(), _target2.GetOneMessage()));
+                    _source.AddMessage(Tuple.Create(_target1!.GetOneMessage(), _target2!.GetOneMessage()));
                 },
                 exception =>
                 {
-                    Volatile.Write(ref _sharedResources._hasExceptions, true);
+                    Volatile.Write(ref _sharedResources!._hasExceptions, true);
                     _source.AddException(exception);
                 },
                 dataflowBlockOptions);
@@ -297,10 +297,10 @@ public JoinBlock(GroupingDataflowBlockOptions dataflowBlockOptions)
             // Configure the targets
             var targets = new JoinBlockTargetBase[3];
             _sharedResources = new JoinBlockTargetSharedResources(this, targets,
-                () => _source.AddMessage(Tuple.Create(_target1.GetOneMessage(), _target2.GetOneMessage(), _target3.GetOneMessage())),
+                () => _source.AddMessage(Tuple.Create(_target1!.GetOneMessage(), _target2!.GetOneMessage(), _target3!.GetOneMessage())),
                 exception =>
                 {
-                    Volatile.Write(ref _sharedResources._hasExceptions, true);
+                    Volatile.Write(ref _sharedResources!._hasExceptions, true);
                     _source.AddException(exception);
                 },
                 dataflowBlockOptions);
@@ -660,7 +660,7 @@ internal override bool ConsumeReservedMessage()
             Debug.Assert(_nonGreedy!.ReservedMessage.Key != null, "This target must have a reserved message");
 
             bool consumed;
-            T consumedValue = _nonGreedy.ReservedMessage.Key.ConsumeMessage(_nonGreedy.ReservedMessage.Value, this, out consumed);
+            T? consumedValue = _nonGreedy.ReservedMessage.Key.ConsumeMessage(_nonGreedy.ReservedMessage.Value, this, out consumed);
 
             // Null out our reservation
             _nonGreedy.ReservedMessage = default(KeyValuePair<ISourceBlock<T>, DataflowMessageHeader>);
@@ -721,7 +721,7 @@ internal override bool ConsumeOnePostponedMessage()
 
                 // Try to consume the popped message
                 bool consumed;
-                T consumedValue = next.Key.ConsumeMessage(next.Value, this, out consumed);
+                T? consumedValue = next.Key.ConsumeMessage(next.Value, this, out consumed);
                 if (consumed)
                 {
                     lock (_sharedResources.IncomingLock)
@@ -861,7 +861,7 @@ DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader message
                         Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                         bool consumed;
-                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed);
+                        messageValue = source.ConsumeMessage(messageHeader, this, out consumed)!;
                         if (!consumed) return DataflowMessageStatus.NotAvailable;
                     }
                     if (_sharedResources._boundingState != null && HasTheHighestNumberOfMessagesAvailable) _sharedResources._boundingState.CurrentCount += 1; // track this new item against our bound
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/TransformBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/TransformBlock.cs
index b5267ca256814..8b95bc4ec0737 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/TransformBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/TransformBlock.cs
@@ -171,7 +171,7 @@ private TransformBlock(Func<TInput, TOutput>? transformSync, Func<TInput, Task<T
         private void ProcessMessage(Func<TInput, TOutput> transform, KeyValuePair<TInput, long> messageWithId)
         {
             // Process the input message to get the output message
-            TOutput outputItem = default(TOutput);
+            TOutput? outputItem = default(TOutput);
             bool itemIsValid = false;
             try
             {
@@ -272,7 +272,7 @@ private void AsyncCompleteProcessMessageWithTask(Task<TOutput> completed, KeyVal
 
             bool isBounded = _target.IsBounded;
             bool gotOutputItem = false;
-            TOutput outputItem = default(TOutput);
+            TOutput? outputItem = default(TOutput);
 
             switch (completed.Status)
             {
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/WriteOnceBlock.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/WriteOnceBlock.cs
index 244703a9d8953..8a6d96cf04cd9 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/WriteOnceBlock.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Blocks/WriteOnceBlock.cs
@@ -287,7 +287,7 @@ bool IReceivableSourceBlock<T>.TryReceiveAll([NotNullWhen(true)] out IList<T>? i
             // Try to receive the one item this block may have.
             // If we can, give back an array of one item. Otherwise,
             // give back null.
-            T item;
+            T? item;
             if (TryReceive(null, out item))
             {
                 items = new T[] { item };
@@ -357,7 +357,7 @@ DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader message
                 if (consumeToAccept)
                 {
                     bool consumed;
-                    messageValue = source!.ConsumeMessage(messageHeader, this, out consumed);
+                    messageValue = source!.ConsumeMessage(messageHeader, this, out consumed)!;
                     if (!consumed) return DataflowMessageStatus.NotAvailable;
                 }
 
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/ProducerConsumerQueues.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/ProducerConsumerQueues.cs
index 0a3ff08ceec78..24b2640ecbbd5 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/ProducerConsumerQueues.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/ProducerConsumerQueues.cs
@@ -79,7 +79,7 @@ internal sealed class MultiProducerMultiConsumerQueue<T> : ConcurrentQueue<T>, I
         /// <summary>Attempts to dequeue an item from the queue.</summary>
         /// <param name="result">The dequeued item.</param>
         /// <returns>true if an item could be dequeued; otherwise, false.</returns>
-        bool IProducerConsumerQueue<T>.TryDequeue(out T result) { return base.TryDequeue(out result); }
+        bool IProducerConsumerQueue<T>.TryDequeue([MaybeNullWhen(false)] out T result) { return base.TryDequeue(out result); }
 
         /// <summary>Gets whether the collection is currently empty.</summary>
         bool IProducerConsumerQueue<T>.IsEmpty { get { return base.IsEmpty; } }
@@ -270,7 +270,7 @@ private bool TryDequeueSlow(ref Segment segment, ref T[] array, [MaybeNullWhen(f
         /// <summary>Attempts to peek at an item in the queue.</summary>
         /// <param name="result">The peeked item.</param>
         /// <returns>true if an item could be peeked; otherwise, false.</returns>
-        public bool TryPeek(out T result)
+        public bool TryPeek([MaybeNullWhen(false)] out T result)
         {
             Segment segment = _head;
             T[] array = segment._array;
@@ -400,8 +400,7 @@ private bool TryDequeueIfSlow(Predicate<T>? predicate, ref Segment segment, ref
 
         public void Clear()
         {
-            T ignored;
-            while (TryDequeue(out ignored)) ;
+            while (TryDequeue(out _)) ;
         }
 
         /// <summary>Gets whether the collection is currently empty.</summary>
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SourceCore.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SourceCore.cs
index a9e86e683c282..780e8ab4e684d 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SourceCore.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SourceCore.cs
@@ -161,7 +161,7 @@ internal IDisposable LinkTo(ITargetBlock<TOutput> target, DataflowLinkOptions li
             if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, nameof(messageHeader));
             if (target == null) throw new ArgumentNullException(nameof(target));
 
-            TOutput consumedMessageValue = default(TOutput);
+            TOutput? consumedMessageValue = default(TOutput);
 
             lock (OutgoingLock)
             {
@@ -336,7 +336,7 @@ internal bool TryReceiveAll([NotNullWhen(true)] out IList<TOutput>? items)
                         {
                             // Receive all of the data, clearing it out in the process.
                             var tmpList = new List<TOutput>();
-                            TOutput item;
+                            TOutput? item;
                             while (_messages.TryDequeue(out item)) tmpList.Add(item);
                             countReceived = tmpList.Count;
                             items = tmpList;
@@ -543,7 +543,7 @@ private bool OfferToTargets(ITargetBlock<TOutput>? linkToTarget = null)
 
             // Peek at the next message if there is one, so we can offer it.
             DataflowMessageHeader header = default(DataflowMessageHeader);
-            TOutput message = default(TOutput);
+            TOutput? message = default(TOutput);
             bool offerJustToLinkToTarget = false;
 
             // If offering isn't enabled and if we're not doing this as
@@ -571,7 +571,7 @@ private bool OfferToTargets(ITargetBlock<TOutput>? linkToTarget = null)
                     // If we've already offered the message to everyone else,
                     // we can just offer it to the newly linked target
                     Debug.Assert(linkToTarget != null, "Must have a valid target to offer to.");
-                    OfferMessageToTarget(header, message, linkToTarget, out messageWasAccepted);
+                    OfferMessageToTarget(header, message!, linkToTarget, out messageWasAccepted);
                 }
                 else
                 {
@@ -590,7 +590,7 @@ private bool OfferToTargets(ITargetBlock<TOutput>? linkToTarget = null)
                     while (cur != null)
                     {
                         TargetRegistry<TOutput>.LinkedTargetInfo? next = cur.Next;
-                        if (OfferMessageToTarget(header, message, cur.Target, out messageWasAccepted)) break;
+                        if (OfferMessageToTarget(header, message!, cur.Target, out messageWasAccepted)) break;
                         cur = next;
                     }
 
@@ -615,7 +615,7 @@ private bool OfferToTargets(ITargetBlock<TOutput>? linkToTarget = null)
                     // even though they weren't supposed to.  To recover from that,
                     // we'll only dequeue if the correct message is still at the head of the queue.
                     // However, we'll assert so that we can at least catch this in our own debug builds.
-                    TOutput dropped;
+                    TOutput? dropped;
                     if (_nextMessageId.Value != header.Id ||
                         !_messages.TryDequeue(out dropped)) // remove the next message
                     {
@@ -643,7 +643,7 @@ private bool OfferToTargets(ITargetBlock<TOutput>? linkToTarget = null)
                 // Notify the owner block that our count has decreased
                 if (_itemsRemovedAction != null)
                 {
-                    int count = _itemCountingFunc != null ? _itemCountingFunc(_owningSource, message, null) : 1;
+                    int count = _itemCountingFunc != null ? _itemCountingFunc(_owningSource, message!, null) : 1;
                     _itemsRemovedAction(_owningSource, count);
                 }
             }
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SpscTargetCore.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SpscTargetCore.cs
index 86762e7ee87bc..d2215b3d9336e 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SpscTargetCore.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/SpscTargetCore.cs
@@ -140,7 +140,7 @@ private DataflowMessageStatus OfferMessage_Slow(DataflowMessageHeader messageHea
             {
                 if (source == null) throw new ArgumentException(SR.Argument_CantConsumeFromANullSource, nameof(consumeToAccept));
                 bool consumed;
-                messageValue = source.ConsumeMessage(messageHeader, _owningTarget, out consumed);
+                messageValue = source.ConsumeMessage(messageHeader, _owningTarget, out consumed)!;
                 if (!consumed) return DataflowMessageStatus.NotAvailable;
             }
 
@@ -203,7 +203,7 @@ private void ProcessMessagesLoopCore()
             while (continueProcessing)
             {
                 continueProcessing = false;
-                TInput nextMessage = default(TInput);
+                TInput? nextMessage = default(TInput);
                 try
                 {
                     // While there are more messages to be processed, process each one.
@@ -253,7 +253,7 @@ private void ProcessMessagesLoopCore()
                         else
                         {
                             // Mark that we're exiting.
-                            Task? previousConsumer = Interlocked.Exchange(ref _activeConsumer, null);
+                            Task? previousConsumer = Interlocked.Exchange<Task?>(ref _activeConsumer, null);
                             Debug.Assert(previousConsumer != null && previousConsumer.Id == Task.CurrentId,
                                 "The running task should have been denoted as the active task.");
 
@@ -325,7 +325,7 @@ private void CompleteBlockOncePossible()
             Debug.Assert(_completionReserved, "Should only invoke once completion has been reserved.");
 
             // Dump any messages that might remain in the queue, which could happen if we completed due to exceptions.
-            TInput dumpedMessage;
+            TInput? dumpedMessage;
             while (_messages.TryDequeue(out dumpedMessage)) ;
 
             // Complete the completion task
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/TargetCore.cs b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/TargetCore.cs
index 844fb108a1bec..e5c00ef9d2858 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/TargetCore.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/Internal/TargetCore.cs
@@ -207,7 +207,7 @@ internal DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader,
                         Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
 
                         bool consumed;
-                        messageValue = source.ConsumeMessage(messageHeader, _owningTarget, out consumed);
+                        messageValue = source.ConsumeMessage(messageHeader, _owningTarget, out consumed)!;
                         if (!consumed) return DataflowMessageStatus.NotAvailable;
                     }
 
@@ -661,7 +661,7 @@ private bool TryConsumePostponedMessage(
                 } // Must not call to source while holding lock
 
                 bool consumed;
-                TInput consumedValue = element.Key.ConsumeMessage(element.Value, _owningTarget, out consumed);
+                TInput? consumedValue = element.Key.ConsumeMessage(element.Value, _owningTarget, out consumed);
                 if (consumed)
                 {
                     result = new KeyValuePair<TInput, long>(consumedValue!, messageId);
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/src/System.Threading.Tasks.Dataflow.csproj b/src/libraries/System.Threading.Tasks.Dataflow/src/System.Threading.Tasks.Dataflow.csproj
index ffb871269eee7..7842613c0ae01 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/src/System.Threading.Tasks.Dataflow.csproj
+++ b/src/libraries/System.Threading.Tasks.Dataflow/src/System.Threading.Tasks.Dataflow.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard1.0;netstandard1.1;net461</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.0;netstandard1.0;netstandard1.1;net461</TargetFrameworks>
+    <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
     <Nullable>enable</Nullable>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -60,7 +61,16 @@
   <ItemGroup>
     <Content Include="XmlDocs\System.Threading.Tasks.Dataflow.xml" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' != 'netstandard2.0'">
+  <ItemGroup Condition="$([MSBuild]::GetTargetFrameworkIdentifier('$(TargetFramework)')) == '.NETCoreApp'">
+    <Reference Include="System.Collections" />
+    <Reference Include="System.Collections.Concurrent" />
+    <Reference Include="System.Linq" />
+    <Reference Include="System.Runtime" />
+    <Reference Include="System.Threading" />
+    <Reference Include="System.Threading.Thread" />
+    <Reference Include="System.Threading.ThreadPool" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.0' or '$(TargetFramework)' == 'netstandard1.1' or $(TargetFramework.StartsWith('net4'))">
     <PackageReference Include="System.Diagnostics.Contracts" Version="$(SystemDiagnosticsContractsVersion)" />
     <PackageReference Include="System.Dynamic.Runtime" Version="$(SystemDynamicRuntimeVersion)" />
     <PackageReference Include="System.Runtime.Serialization.Primitives" Version="$(SystemRuntimeSerializationPrimitivesVersion)" />