이 예제에서는 Wait 메서드 또는 Task<TResult> 클래스의 해당 메서드를 사용하여 단일 작업에서 대기하는 방법을 보여 줍니다. 또한 정적 WaitAll 및 WaitAny 메서드를 사용하여 여러 작업에서 대기하는 방법도 보여 줍니다.
예제
' How to: Wait on One or More Tasks to Complete
Imports System.Threading
Imports System.Threading.Tasks
Module WaitOnTasks
Dim rand As New Random()
Sub Main()
' Wait on a single task with no timeout specified.
Dim taskA = Task.Factory.StartNew(Sub() DoSomeWork(10000000))
taskA.Wait()
Console.WriteLine("taskA has completed.")
' Wait on a single task with a timeout specified.
Dim taskB = Task.Factory.StartNew(Sub() DoSomeWork(10000000))
taskB.Wait(100) 'Wait for 100 ms.
If (taskB.IsCompleted) Then
Console.WriteLine("taskB has completed.")
Else
Console.WriteLine("Timed out before task2 completed.")
End If
' Wait for all tasks to complete.
Dim myTasks(9) As Task
For i As Integer = 0 To myTasks.Length - 1
myTasks(i) = Task.Factory.StartNew(Sub() DoSomeWork(10000000))
Next
Task.WaitAll(myTasks)
' Wait for first task to complete.
Dim tasks2(2) As Task(Of Double)
' Try three different approaches to the problem. Take the first one.
tasks2(0) = Task(Of Double).Factory.StartNew(Function() TrySolution1())
tasks2(1) = Task(Of Double).Factory.StartNew(Function() TrySolution2())
tasks2(2) = Task(Of Double).Factory.StartNew(Function() TrySolution3())
Dim index As Integer = Task.WaitAny(tasks2)
Dim d As Double = tasks2(index).Result
Console.WriteLine("task(0) completed first with result of {1}.", index, d)
Console.ReadKey()
End Sub
' Dummy Functions to Simulate Work
Function DoSomeWork(ByVal val As Integer)
' Pretend to do something.
Thread.SpinWait(val)
End Function
Function TrySolution1()
Dim i As Integer = rand.Next(1000000)
' Simulate work by spinning
Thread.SpinWait(i)
Return i
End Function
Function TrySolution2()
Dim i As Integer = rand.Next(1000000)
' Simulate work by spinning
Thread.SpinWait(i)
Return i
End Function
Function TrySolution3()
Dim i As Integer = rand.Next(1000000)
' Simulate work by spinning
Thread.SpinWait(i)
Thread.SpinWait(1000000)
Return i
End Function
End Module
using System;
using System.Threading;
using System.Threading.Tasks;
class Program
{
static Random rand = new Random();
static void Main(string[] args)
{
// Wait on a single task with no timeout specified.
Task taskA = Task.Factory.StartNew(() => DoSomeWork(10000000));
taskA.Wait();
Console.WriteLine("taskA has completed.");
// Wait on a single task with a timeout specified.
Task taskB = Task.Factory.StartNew(() => DoSomeWork(10000000));
taskB.Wait(100); //Wait for 100 ms.
if (taskB.IsCompleted)
Console.WriteLine("taskB has completed.");
else
Console.WriteLine("Timed out before taskB completed.");
// Wait for all tasks to complete.
Task[] tasks = new Task[10];
for (int i = 0; i < 10; i++)
{
tasks[i] = Task.Factory.StartNew(() => DoSomeWork(10000000));
}
Task.WaitAll(tasks);
// Wait for first task to complete.
Task<double>[] tasks2 = new Task<double>[3];
// Try three different approaches to the problem. Take the first one.
tasks2[0] = Task<double>.Factory.StartNew(() => TrySolution1());
tasks2[1] = Task<double>.Factory.StartNew(() => TrySolution2());
tasks2[2] = Task<double>.Factory.StartNew(() => TrySolution3());
int index = Task.WaitAny(tasks2);
double d = tasks2[index].Result;
Console.WriteLine("task[{0}] completed first with result of {1}.", index, d);
Console.ReadKey();
}
static void DoSomeWork(int val)
{
// Pretend to do something.
Thread.SpinWait(val);
}
static double TrySolution1()
{
int i = rand.Next(1000000);
// Simulate work by spinning
Thread.SpinWait(i);
return DateTime.Now.Millisecond;
}
static double TrySolution2()
{
int i = rand.Next(1000000);
// Simulate work by spinning
Thread.SpinWait(i);
return DateTime.Now.Millisecond;
}
static double TrySolution3()
{
int i = rand.Next(1000000);
// Simulate work by spinning
Thread.SpinWait(i);
Thread.SpinWait(1000000);
return DateTime.Now.Millisecond;
}
}
편의상 이 예제에서는 예외 처리 코드나 취소 코드는 보여 주지 않습니다. 대부분의 경우 대기는 작업에서 발생하는 예외를 프로그램 코드에서 처리하는 데 사용되는 메커니즘이므로 Wait 메서드를 try-catch 블록 안에 넣어야 합니다. 자세한 내용은 방법: 작업에서 throw된 예외 처리를 참조하십시오. 작업이 취소 가능한 경우 작업 또는 작업의 Result() 속성을 사용하기 전에 IsCanceled 또는 IsCancellationRequested() 속성을 확인해야 합니다. 자세한 내용은 방법: 작업 및 해당 자식 취소를 참조하십시오.