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-rw-r--r--src/mscorlib/shared/System/Threading/Tasks/TaskExtensions.cs48
1 files changed, 48 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Threading/Tasks/TaskExtensions.cs b/src/mscorlib/shared/System/Threading/Tasks/TaskExtensions.cs
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+++ b/src/mscorlib/shared/System/Threading/Tasks/TaskExtensions.cs
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+// 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.
+
+namespace System.Threading.Tasks
+{
+ /// <summary>Provides a set of static methods for working with specific kinds of <see cref="Task"/> instances.</summary>
+ public static class TaskExtensions
+ {
+ /// <summary>Creates a proxy <see cref="Task"/> that represents the asynchronous operation of a <see cref="Task{Task}"/>.</summary>
+ /// <param name="task">The <see cref="Task{Task}"/> to unwrap.</param>
+ /// <returns>A <see cref="Task"/> that represents the asynchronous operation of the provided <see cref="Task{Task}"/>.</returns>
+ public static Task Unwrap(this Task<Task> task)
+ {
+ if (task == null)
+ {
+ throw new ArgumentNullException(nameof(task));
+ }
+
+ // If the task hasn't completed or was faulted/canceled, wrap it in an unwrap promise. Otherwise,
+ // it completed successfully. Return its inner task to avoid unnecessary wrapping, or if the inner
+ // task is null, return a canceled task to match the same semantics as CreateUnwrapPromise.
+ return
+ !task.IsRanToCompletion ? Task.CreateUnwrapPromise<VoidTaskResult>(task, lookForOce: false) :
+ task.Result ??
+ Task.FromCanceled(new CancellationToken(true));
+ }
+
+ /// <summary>Creates a proxy <see cref="Task{TResult}"/> that represents the asynchronous operation of a <see cref="Task{Task{TResult}}"/>.</summary>
+ /// <param name="task">The <see cref="Task{Task{TResult}}"/> to unwrap.</param>
+ /// <returns>A <see cref="Task{TResult}"/> that represents the asynchronous operation of the provided <see cref="Task{Task{TResult}}"/>.</returns>
+ public static Task<TResult> Unwrap<TResult>(this Task<Task<TResult>> task)
+ {
+ if (task == null)
+ {
+ throw new ArgumentNullException(nameof(task));
+ }
+
+ // If the task hasn't completed or was faulted/canceled, wrap it in an unwrap promise. Otherwise,
+ // it completed successfully. Return its inner task to avoid unnecessary wrapping, or if the inner
+ // task is null, return a canceled task to match the same semantics as CreateUnwrapPromise.
+ return
+ !task.IsRanToCompletion ? Task.CreateUnwrapPromise<TResult>(task, lookForOce: false) :
+ task.Result ??
+ Task.FromCanceled<TResult>(new CancellationToken(true));
+ }
+ }
+}