Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

mcs/class/System.Threading.Tasks.Dataflow/CoreFxSources/Base/IReceivableSourceBlock.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// IReceivableSourceBlock.cs
+//
+//
+// The base interface for all source blocks.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections.Generic;
+
+namespace System.Threading.Tasks.Dataflow
+{
+    /// <summary>Represents a dataflow block that supports receiving of messages without linking.</summary>
+    /// <typeparam name="TOutput">Specifies the type of data supplied by the <see cref="IReceivableSourceBlock{TOutput}"/>.</typeparam>
+    public interface IReceivableSourceBlock<TOutput> : ISourceBlock<TOutput>
+    {
+        // IMPLEMENT IMPLICITLY
+
+        /// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceive"]/*' />
+        bool TryReceive(Predicate<TOutput> filter, out TOutput item);
+
+        // IMPLEMENT IMPLICITLY IF BLOCK SUPPORTS RECEIVING MORE THAN ONE ITEM, OTHERWISE EXPLICITLY
+
+        /// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceiveAll"]/*' />
+        bool TryReceiveAll(out IList<TOutput> items);
+    }
+}