WhenAll Method (IEnumerable(Task))

Task.WhenAll Method (IEnumerable<Task>)

.NET Framework 4.6 and 4.5

Creates a task that will complete when all of the Task objects in an enumerable collection have completed.

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

public static Task WhenAll(
	IEnumerable<Task> tasks


Type: System.Collections.Generic.IEnumerable<Task>

The tasks to wait on for completion.

Return Value

Type: System.Threading.Tasks.Task

A task that represents the completion of all of the supplied tasks.

Exception Condition

The tasks argument was null.


The tasks collection contained a null task.

If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.

If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.

If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state.

If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion state before it's returned to the caller.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.5
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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