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

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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)

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Unwrap(Of TResult) ( _
    task As Task(Of Task(Of TResult)) _
) As Task(Of TResult)

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

Type Parameters

  • TResult
    The type of the task's result.

Parameters

Return Value

Type: System.Threading.Tasks.Task<TResult>
A [System.Threading.Tasks.Task`1] 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.

Exceptions

Exception Condition
ArgumentNullException

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

Remarks

It is often useful to be able to return a [System.Threading.Tasks.Task`1] from a [System.Threading.Tasks.Task`1], where the inner [System.Threading.Tasks.Task`1] represents work done as part of the outer [System.Threading.Tasks.Task`1]. 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 [System.Threading.Tasks.Task`1] that represents the entire asynchronous operation of such a Task<Task<T>> (C#) or Task (Of Task(Of T)) (Visual Basic).

Version Information

Silverlight

Supported in: 5

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.