Imported Upstream version 6.4.0.137

Former-commit-id: 943baa9f16a098c33e129777827f3a9d20da00d6

mcs/class/corlib/corefx/TaskAsyncEnumerableExtensions.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>Provides a set of static methods for configuring <see cref="Task"/>-related behaviors on asynchronous enumerables and disposables.</summary>
+    public static class TaskAsyncEnumerableExtensions
+    {
+        /// <summary>Configures how awaits on the tasks returned from an async disposable will be performed.</summary>
+        /// <param name="source">The source async disposable.</param>
+        /// <param name="continueOnCapturedContext">Whether to capture and marshal back to the current context.</param>
+        /// <returns>The configured async disposable.</returns>
+        public static ConfiguredAsyncDisposable ConfigureAwait(this IAsyncDisposable source, bool continueOnCapturedContext) =>
+            new ConfiguredAsyncDisposable(source, continueOnCapturedContext);
+
+        /// <summary>Configures how awaits on the tasks returned from an async iteration will be performed.</summary>
+        /// <typeparam name="T">The type of the objects being iterated.</typeparam>
+        /// <param name="source">The source enumerable being iterated.</param>
+        /// <param name="continueOnCapturedContext">Whether to capture and marshal back to the current context.</param>
+        /// <returns>The configured enumerable.</returns>
+        public static ConfiguredCancelableAsyncEnumerable<T> ConfigureAwait<T>(
+            this IAsyncEnumerable<T> source, bool continueOnCapturedContext) =>
+            new ConfiguredCancelableAsyncEnumerable<T>(source, continueOnCapturedContext, cancellationToken: default);
+
+        /// <summary>Sets the <see cref="CancellationToken"/> to be passed to <see cref="IAsyncEnumerable{T}.GetAsyncEnumerator(CancellationToken)"/> when iterating.</summary>
+        /// <typeparam name="T">The type of the objects being iterated.</typeparam>
+        /// <param name="source">The source enumerable being iterated.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> to use.</param>
+        /// <returns>The configured enumerable.</returns>
+        public static ConfiguredCancelableAsyncEnumerable<T> WithCancellation<T>(
+            this IAsyncEnumerable<T> source, CancellationToken cancellationToken) =>
+            new ConfiguredCancelableAsyncEnumerable<T>(source, continueOnCapturedContext: true, cancellationToken);
+    }
+}