TaskExtensions.Unwrap<TResult> Method (Task<Task<TResult>>)

May 11, 2014

Creates a proxy Task that represents the asynchronous operation of a Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic).

Namespace:  System.Threading.Tasks
Assembly:  System.Core (in System.Core.dll)

public static Task<TResult> Unwrap<TResult>(
	this Task<Task<TResult>> task
)

Type Parameters

TResult

The type of the task's result.

Parameters

task
Type: System.Threading.Tasks.Task<Task<TResult>>
The Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic) to unwrap.

Return Value

Type: System.Threading.Tasks.Task<TResult>
A Task that represents the asynchronous operation of the provided Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic).

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type Task<Task<TResult>>. When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

The exception that is thrown if the task argument is null.

It is often useful to be able to return a Task from a Task, where the inner Task represents work done as part of the outer Task. However, doing so results in a Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic), which, if not dealt with carefully, could produce unexpected behavior. Unwrap solves this problem by creating a proxy Task<TResult> that represents the entire asynchronous operation of such a Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic).

Windows Phone OS

Supported in: 8.1, 8.0

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