Task.WaitAll
Method
Definition
Overloads
| WaitAll(Task[]) |
Waits for all of the provided Task objects to complete execution. |
| 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) |
Waits for all of the provided Task objects to complete execution within a specified number of milliseconds or until the wait is cancelled. |
WaitAll(Task[])
Waits for all of the provided Task objects to complete execution.
public static void WaitAll (params System.Threading.Tasks.Task[] tasks);
One or more of the Task objects in tasks has been disposed.
The tasks argument is null.
The tasks argument contains a null element.
-or-
The tasks argument is an empty array.
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()
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()
WaitAll(Task[], Int32)
Waits for all of the provided Task objects to complete execution within a specified number of milliseconds.
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout);
- millisecondsTimeout
- Int32
The number of milliseconds to wait, or Infinite (-1) to wait indefinitely.
true if all of the Task instances completed execution within the allotted time; otherwise, false.
One or more of the Task objects in tasks has been disposed.
The tasks argument is null.
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.
millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.
The tasks argument contains a null element.
-or-
The tasks argument is an empty array.
WaitAll(Task[], CancellationToken)
Waits for all of the provided Task objects to complete execution unless the wait is cancelled.
public static void WaitAll (System.Threading.Tasks.Task[] tasks, System.Threading.CancellationToken cancellationToken);
- cancellationToken
- CancellationToken
A CancellationToken to observe while waiting for the tasks to complete.
The cancellationToken was canceled.
The tasks argument is null.
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.
The tasks argument contains a null element.
-or-
The tasks argument is an empty array.
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.
WaitAll(Task[], TimeSpan)
Waits for all of the provided cancellable Task objects to complete execution within a specified time interval.
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, TimeSpan timeout);
- timeout
- TimeSpan
A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds to wait indefinitely.
true if all of the Task instances completed execution within the allotted time; otherwise, false.
One or more of the Task objects in tasks has been disposed.
The tasks argument is null.
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.
timeout is a negative number other than -1 milliseconds, which represents an infinite time-out.
-or-
timeout is greater than MaxValue.
The tasks argument contains a null element.
-or-
The tasks argument is an empty array.
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.
public static bool WaitAll (System.Threading.Tasks.Task[] tasks, int millisecondsTimeout, System.Threading.CancellationToken cancellationToken);
- 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.
true if all of the Task instances completed execution within the allotted time; otherwise, false.
One or more of the Task objects in tasks has been disposed.
The tasks argument is null.
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.
millisecondsTimeout is a negative number other than -1, which represents an infinite time-out.
The tasks argument contains a null element.
-or-
The tasks argument is an empty array.
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.