Task.WaitAll Method

Reference

Definition

Namespace:: System.Threading.Tasks

Assembly:: System.Threading.Tasks.dll

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Waits for all of the provided Task objects to complete execution.

Overloads

WaitAll(Task[], Int32, CancellationToken)	Waits for all of the provided Task objects to complete execution within a specified number of milliseconds or until the wait is cancelled.
WaitAll(ReadOnlySpan<Task>)	Waits for all of the provided Task objects to complete execution.
WaitAll(Task[])	Waits for all of the provided Task objects to complete execution.
WaitAll(IEnumerable<Task>, CancellationToken)	Waits for all of the provided Task objects to complete execution unless the wait is cancelled.
WaitAll(Task[], Int32)	Waits for all of the provided Task objects to complete execution within a specified number of milliseconds.
WaitAll(Task[], CancellationToken)	Waits for all of the provided Task objects to complete execution unless the wait is cancelled.
WaitAll(Task[], TimeSpan)	Waits for all of the provided cancellable Task objects to complete execution within a specified time interval.

WaitAll(Task[], Int32, CancellationToken)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Waits for all of the provided Task objects to complete execution within a specified number of milliseconds or until the wait is cancelled.

public:
 static bool WaitAll(cli::array <System::Threading::Tasks::Task ^> ^ tasks, int millisecondsTimeout, System::Threading::CancellationToken cancellationToken);

public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout, System.Threading.CancellationToken cancellationToken);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout, System.Threading.CancellationToken cancellationToken);

static member WaitAll : System.Threading.Tasks.Task[] * int * System.Threading.CancellationToken -> bool

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : System.Threading.Tasks.Task[] * int * System.Threading.CancellationToken -> bool

Public Shared Function WaitAll (tasks As Task(), millisecondsTimeout As Integer, cancellationToken As CancellationToken) As Boolean

Parameters

tasks: Task[]

An array of Task instances on which to wait.

millisecondsTimeout: Int32

The number of milliseconds to wait, or Infinite (-1) to wait indefinitely.

cancellationToken: CancellationToken

A CancellationToken to observe while waiting for the tasks to complete.

Returns

Boolean

true if all of the Task instances completed execution within the allotted time; otherwise, false.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

ArgumentNullException

The tasks argument is null.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.

-or-

An exception was thrown during the execution of at least one of the Task instances.

ArgumentOutOfRangeException

millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.

ArgumentException

The tasks argument contains a null element.

OperationCanceledException

The cancellationToken was canceled.

Remarks

The cancellationToken argument is used to cancel the wait operation. Cancellation of the tasks is a distinct operation, and is signaled by the AggregateException noted above.

Applies to

WaitAll(ReadOnlySpan<Task>)

Waits for all of the provided Task objects to complete execution.

public:
 static void WaitAll(ReadOnlySpan<System::Threading::Tasks::Task ^> tasks);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static void WaitAll (scoped ReadOnlySpan<System.Threading.Tasks.Task> tasks);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : ReadOnlySpan<System.Threading.Tasks.Task> -> unit

Public Shared Sub WaitAll (tasks As ReadOnlySpan(Of Task))

Parameters

tasks: ReadOnlySpan<Task>

An array of Task instances on which to wait.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ArgumentNullException

The tasks argument contains a null element.

AggregateException

At least one of the Task instances was canceled.

-or-

An exception was thrown during the execution of at least one of the Task instances.

Applies to

WaitAll(Task[])

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Waits for all of the provided Task objects to complete execution.

public:
 static void WaitAll(... cli::array <System::Threading::Tasks::Task ^> ^ tasks);

public static void WaitAll (params System.Threading.Tasks.Task[] tasks);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static void WaitAll (params System.Threading.Tasks.Task[] tasks);

static member WaitAll : System.Threading.Tasks.Task[] -> unit

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : System.Threading.Tasks.Task[] -> unit

Public Shared Sub WaitAll (ParamArray tasks As Task())

Parameters

tasks: Task[]

An array of Task instances on which to wait.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

ArgumentNullException

The tasks argument is null.

ArgumentException

The tasks argument contains a null element.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException exception contains an OperationCanceledException exception in its InnerExceptions collection.

-or-

An exception was thrown during the execution of at least one of the Task instances.

Examples

The following example starts 10 tasks, each of which is passed an index as a state object. Tasks with an index from two to five throw exceptions. The call to the WaitAll method wraps all exceptions in an AggregateException object and propagates it to the calling thread.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

class Example
{
    static void Main()
    {
        var tasks = new List<Task<int>>();
         
        // Define a delegate that prints and returns the system tick count
        Func<object, int> action = (object obj) =>
        {
            int i = (int)obj;

            // Make each thread sleep a different time in order to return a different tick count
            Thread.Sleep(i * 100);

            // The tasks that receive an argument between 2 and 5 throw exceptions
            if (2 <= i && i <= 5)
            {
                throw new InvalidOperationException("SIMULATED EXCEPTION");
            }

            int tickCount = Environment.TickCount;
            Console.WriteLine("Task={0}, i={1}, TickCount={2}, Thread={3}", Task.CurrentId, i, tickCount, Thread.CurrentThread.ManagedThreadId);

            return tickCount;
        };

        // Construct started tasks
        for (int i = 0; i < 10; i++)
        {
            int index = i;
            tasks.Add(Task<int>.Factory.StartNew(action, index));
        }

        try
        {
            // Wait for all the tasks to finish.
            Task.WaitAll(tasks.ToArray());

            // We should never get to this point
            Console.WriteLine("WaitAll() has not thrown exceptions. THIS WAS NOT EXPECTED.");
        }
        catch (AggregateException e)
        {
            Console.WriteLine("\nThe following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)");
            for (int j = 0; j < e.InnerExceptions.Count; j++)
            {
                Console.WriteLine("\n-------------------------------------------------\n{0}", e.InnerExceptions[j].ToString());
            }
        }
    }
}
// The example displays output like the following:
//     Task=1, i=0, TickCount=1203822250, Thread=3
//     Task=2, i=1, TickCount=1203822359, Thread=4
//     Task=7, i=6, TickCount=1203823484, Thread=3
//     Task=8, i=7, TickCount=1203823890, Thread=4
//     Task=9, i=8, TickCount=1203824296, Thread=3
//     Task=10, i=9, TickCount=1203824796, Thread=4
//     
//     The following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)
//     
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//     
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//     
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//     
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()

open System
open System.Threading
open System.Threading.Tasks

// Define a delegate that prints and returns the system tick count
let action =
    fun (obj: obj) ->
        let i = obj :?> int

        // Make each thread sleep a different time in order to return a different tick count
        Thread.Sleep(i * 100)

        // The tasks that receive an argument between 2 and 5 throw exceptions
        if 2 <= i && i <= 5 then
            raise (InvalidOperationException "SIMULATED EXCEPTION")


        let tickCount = Environment.TickCount
        printfn $"Task={Task.CurrentId}, i={i}, TickCount={tickCount}, Thread={Thread.CurrentThread.ManagedThreadId}"
        tickCount

// Construct started tasks
let tasks =
    [| for i = 0 to 9 do
           Task<int>.Factory.StartNew (action, i) |]

try

    // Wait for all the tasks to finish.
    Seq.cast tasks |> Seq.toArray |> Task.WaitAll

    // We should never get to this point
    printfn "WaitAll() has not thrown exceptions. THIS WAS NOT EXPECTED."

with :? AggregateException as e ->
    printfn "\nThe following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)"

    for ex in e.InnerExceptions do
        printfn $"\n-------------------------------------------------\n{ex}"

// The example displays output like the following:
//     Task=1, i=0, TickCount=1203822250, Thread=3
//     Task=2, i=1, TickCount=1203822359, Thread=4
//     Task=7, i=6, TickCount=1203823484, Thread=3
//     Task=8, i=7, TickCount=1203823890, Thread=4
//     Task=9, i=8, TickCount=1203824296, Thread=3
//     Task=10, i=9, TickCount=1203824796, Thread=4
//
//     The following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)
//
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()
//
//     -------------------------------------------------
//     System.InvalidOperationException: SIMULATED EXCEPTION
//        at Example.<Main>b__0(Object obj)
//        at System.Threading.Tasks.Task`1.InnerInvoke()
//        at System.Threading.Tasks.Task.Execute()

Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module WaitAllDemo
    Sub Main()
        Dim tasks As New List(Of Task(Of Integer))()
        ' Define a delegate that prints and returns the system tick count
        Dim action As Func(Of Object, Integer) = Function(obj As Object)
                                                     Dim i As Integer = CInt(obj)

                                                     ' Make each thread sleep a different time in order to return a different tick count
                                                     Thread.Sleep(i * 100)

                                                     ' The tasks that receive an argument between 2 and 5 throw exceptions
                                                     If 2 <= i AndAlso i <= 5 Then
                                                         Throw New InvalidOperationException("SIMULATED EXCEPTION")
                                                     End If

                                                     Dim tickCount As Integer = Environment.TickCount
                                                     Console.WriteLine("Task={0}, i={1}, TickCount={2}, Thread={3}", Task.CurrentId, i, tickCount, Thread.CurrentThread.ManagedThreadId)

                                                     Return tickCount
                                                 End Function

        ' Construct started tasks
        For i As Integer = 0 To 9
            Dim index As Integer = i
            tasks.Add(Task(Of Integer).Factory.StartNew(action, index))
        Next

        Try
            ' Wait for all the tasks to finish.
            Task.WaitAll(tasks.ToArray())

            ' We should never get to this point
            Console.WriteLine("WaitAll() has not thrown exceptions. THIS WAS NOT EXPECTED.")
        Catch e As AggregateException
            Console.WriteLine(vbLf & "The following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)")
            For j As Integer = 0 To e.InnerExceptions.Count - 1
                Console.WriteLine(vbLf & "-------------------------------------------------" & vbLf & "{0}", e.InnerExceptions(j).ToString())
            Next
        End Try
    End Sub
End Module
' The example displays output like the following:
'     Task=1, i=0, TickCount=1203822250, Thread=3
'     Task=2, i=1, TickCount=1203822359, Thread=4
'     Task=7, i=6, TickCount=1203823484, Thread=3
'     Task=8, i=7, TickCount=1203823890, Thread=4
'     Task=9, i=8, TickCount=1203824296, Thread=3
'     Task=10, i=9, TickCount=1203824796, Thread=4
'     
'     The following exceptions have been thrown by WaitAll(): (THIS WAS EXPECTED)
'     
'     -------------------------------------------------
'     System.InvalidOperationException: SIMULATED EXCEPTION
'        at Example.<Main>b__0(Object obj)
'        at System.Threading.Tasks.Task`1.InnerInvoke()
'        at System.Threading.Tasks.Task.Execute()
'     
'     -------------------------------------------------
'     System.InvalidOperationException: SIMULATED EXCEPTION
'        at Example.<Main>b__0(Object obj)
'        at System.Threading.Tasks.Task`1.InnerInvoke()
'        at System.Threading.Tasks.Task.Execute()
'     
'     -------------------------------------------------
'     System.InvalidOperationException: SIMULATED EXCEPTION
'        at Example.<Main>b__0(Object obj)
'        at System.Threading.Tasks.Task`1.InnerInvoke()
'        at System.Threading.Tasks.Task.Execute()
'     
'     -------------------------------------------------
'     System.InvalidOperationException: SIMULATED EXCEPTION
'        at Example.<Main>b__0(Object obj)
'        at System.Threading.Tasks.Task`1.InnerInvoke()
'        at System.Threading.Tasks.Task.Execute()

Applies to

WaitAll(IEnumerable<Task>, CancellationToken)

Waits for all of the provided Task objects to complete execution unless the wait is cancelled.

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static void WaitAll (System.Collections.Generic.IEnumerable<System.Threading.Tasks.Task> tasks, System.Threading.CancellationToken cancellationToken = default);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : seq<System.Threading.Tasks.Task> * System.Threading.CancellationToken -> unit

Public Shared Sub WaitAll (tasks As IEnumerable(Of Task), Optional cancellationToken As CancellationToken = Nothing)

Parameters

tasks: IEnumerable<Task>

A collection of tasks on which to wait.

cancellationToken: CancellationToken

A token to observe while waiting for the tasks to complete.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ArgumentNullException

The tasks argument is null.

ArgumentException

The tasks argument contains a null element.

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

OperationCanceledException

The cancellationToken was canceled.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.

Applies to

WaitAll(Task[], Int32)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Waits for all of the provided Task objects to complete execution within a specified number of milliseconds.

public:
 static bool WaitAll(cli::array <System::Threading::Tasks::Task ^> ^ tasks, int millisecondsTimeout);

public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout);

static member WaitAll : System.Threading.Tasks.Task[] * int -> bool

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : System.Threading.Tasks.Task[] * int -> bool

Public Shared Function WaitAll (tasks As Task(), millisecondsTimeout As Integer) As Boolean

Parameters

tasks: Task[]

An array of Task instances on which to wait.

millisecondsTimeout: Int32

The number of milliseconds to wait, or Infinite (-1) to wait indefinitely.

Returns

Boolean

true if all of the Task instances completed execution within the allotted time; otherwise, false.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

ArgumentNullException

The tasks argument is null.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.

-or-

An exception was thrown during the execution of at least one of the Task instances.

ArgumentOutOfRangeException

millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.

ArgumentException

The tasks argument contains a null element.

Applies to

WaitAll(Task[], CancellationToken)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Waits for all of the provided Task objects to complete execution unless the wait is cancelled.

public:
 static void WaitAll(cli::array <System::Threading::Tasks::Task ^> ^ tasks, System::Threading::CancellationToken cancellationToken);

public static void WaitAll (System.Threading.Tasks.Task[] tasks, System.Threading.CancellationToken cancellationToken);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static void WaitAll (System.Threading.Tasks.Task[] tasks, System.Threading.CancellationToken cancellationToken);

static member WaitAll : System.Threading.Tasks.Task[] * System.Threading.CancellationToken -> unit

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : System.Threading.Tasks.Task[] * System.Threading.CancellationToken -> unit

Public Shared Sub WaitAll (tasks As Task(), cancellationToken As CancellationToken)

Parameters

tasks: Task[]

An array of Task instances on which to wait.

cancellationToken: CancellationToken

A CancellationToken to observe while waiting for the tasks to complete.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

OperationCanceledException

The cancellationToken was canceled.

ArgumentNullException

The tasks argument is null.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.

-or-

An exception was thrown during the execution of at least one of the Task instances.

ArgumentException

The tasks argument contains a null element.

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

Remarks

The cancellationToken argument is used to cancel the wait operation. Cancellation of the tasks is a distinct operation, and is signaled by the AggregateException as noted above.

Applies to

WaitAll(Task[], TimeSpan)

Source:: Task.cs

Source:: Task.cs

Source:: Task.cs

Waits for all of the provided cancellable Task objects to complete execution within a specified time interval.

public:
 static bool WaitAll(cli::array <System::Threading::Tasks::Task ^> ^ tasks, TimeSpan timeout);

public static bool WaitAll (System.Threading.Tasks.Task[] tasks, TimeSpan timeout);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, TimeSpan timeout);

static member WaitAll : System.Threading.Tasks.Task[] * TimeSpan -> bool

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
static member WaitAll : System.Threading.Tasks.Task[] * TimeSpan -> bool

Public Shared Function WaitAll (tasks As Task(), timeout As TimeSpan) As Boolean

Parameters

tasks: Task[]

An array of Task instances on which to wait.

timeout: TimeSpan

A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds to wait indefinitely.

Returns

Boolean

true if all of the Task instances completed execution within the allotted time; otherwise, false.

Attributes: UnsupportedOSPlatformAttribute

Exceptions

ObjectDisposedException

One or more of the Task objects in tasks has been disposed.

ArgumentNullException

The tasks argument is null.

AggregateException

At least one of the Task instances was canceled. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.

-or-

An exception was thrown during the execution of at least one of the Task instances.

ArgumentOutOfRangeException

timeout is a negative number other than -1 milliseconds, which represents an infinite time-out.

-or-

timeout is greater than Int32.MaxValue.

ArgumentException

The tasks argument contains a null element.

Applies to

Share via

Task.WaitAll Method

Definition

Overloads

WaitAll(Task[], Int32, CancellationToken)

Parameters

Returns

Exceptions

Remarks

Applies to

WaitAll(ReadOnlySpan<Task>)

Parameters

Exceptions

Applies to

WaitAll(Task[])

Parameters

Exceptions

Examples

Applies to

WaitAll(IEnumerable<Task>, CancellationToken)

Parameters

Exceptions

Applies to

WaitAll(Task[], Int32)

Parameters

Returns

Exceptions

Applies to

WaitAll(Task[], CancellationToken)

Parameters

Exceptions

Remarks

Applies to

WaitAll(Task[], TimeSpan)

Parameters

Returns

Exceptions

Applies to

Additional resources