我是 C# 的新手;我主要做Java。
我想按照以下方式实现超时:
int now= Time.now();
while(true)
{
tryMethod();
if(now > now+5000) throw new TimeoutException();
}
如何在 C# 中实现这一点?谢谢!
一种可能的方法是:
Stopwatch sw = new Stopwatch();
sw.Start();
while(true)
{
tryMethod();
if(sw.ElapsedMilliseconds > 5000) throw new TimeoutException();
}
但是,您目前无法摆脱循环。我建议tryMethod
返回 abool
并将其更改为:
Stopwatch sw = new Stopwatch();
sw.Start();
while(!tryMethod())
{
if(sw.ElapsedMilliseconds > 5000) throw new TimeoutException();
}
我认为您可以使用计时器和委托来执行此操作,我的示例代码如下:
using System;
using System.Timers;
class Program
{
public delegate void tm();
static void Main(string[] args)
{
var t = new tm(tryMethod);
var timer = new Timer();
timer.Interval = 5000;
timer.Start();
timer.Elapsed += (sender, e) => timer_Elapsed(t);
t.BeginInvoke(null, null);
}
static void timer_Elapsed(tm p)
{
p.EndInvoke(null);
throw new TimeoutException();
}
static void tryMethod()
{
Console.WriteLine("FooBar");
}
}
你有 tryMethod,然后你创建一个委托并将这个委托指向 tryMethod,然后你异步启动这个委托。然后你有一个计时器,间隔为 5000 毫秒,你将你的委托传递给你的计时器经过的方法(它应该作为一个委托是一个引用类型,而不是一个值类型),一旦 5000 秒过去了,你调用 EndInvoke您的委托上的方法。
这个问题很老了,但还有另一种选择。
using(CancellationTokenSource cts = new CancellationTokenSource(5000))
{
cts.Token.Register(() => { throw new TimeoutException(); });
while(!cts.IsCancellationRequested)
{
tryMethod();
}
}
从技术上讲,您还应该传播CancellationToken
intryMethod()
以优雅地中断它。
工作演示:(注意我必须删除异常抛出行为,因为 .netfiddle 不喜欢它。)
只要 tryMethod() 不阻止这应该做你想要的:
移动时夏令时或更改时区不安全:
DateTime startTime = DateTime.Now;
while(true)
{
tryMethod();
if(DateTime.Now.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
时区和夏令时安全版本:
DateTime startTime = DateTime.UtcNow;
while(true)
{
tryMethod();
if(DateTime.UtcNow.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
(DateTimeOffset 需要 .NET 3.5 或更高版本。)
DateTimeOffset startTime = DateTimeOffset.Now;
while(true)
{
tryMethod();
if(DateTimeOffset.Now.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
在这里,我实现了一个自定义类,该类具有包装任务以实现超时的方法。
public class TaskWithTimeoutWrapper
{
protected volatile bool taskFinished = false;
public async Task<T> RunWithCustomTimeoutAsync<T>(int millisecondsToTimeout, Func<Task<T>> taskFunc, CancellationTokenSource cancellationTokenSource = null)
{
this.taskFinished = false;
var results = await Task.WhenAll<T>(new List<Task<T>>
{
this.RunTaskFuncWrappedAsync<T>(taskFunc),
this.DelayToTimeoutAsync<T>(millisecondsToTimeout, cancellationTokenSource)
});
return results[0];
}
public async Task RunWithCustomTimeoutAsync(int millisecondsToTimeout, Func<Task> taskFunc, CancellationTokenSource cancellationTokenSource = null)
{
this.taskFinished = false;
await Task.WhenAll(new List<Task>
{
this.RunTaskFuncWrappedAsync(taskFunc),
this.DelayToTimeoutAsync(millisecondsToTimeout, cancellationTokenSource)
});
}
protected async Task DelayToTimeoutAsync(int millisecondsToTimeout, CancellationTokenSource cancellationTokenSource)
{
await Task.Delay(millisecondsToTimeout);
this.ActionOnTimeout(cancellationTokenSource);
}
protected async Task<T> DelayToTimeoutAsync<T>(int millisecondsToTimeout, CancellationTokenSource cancellationTokenSource)
{
await this.DelayToTimeoutAsync(millisecondsToTimeout, cancellationTokenSource);
return default(T);
}
protected virtual void ActionOnTimeout(CancellationTokenSource cancellationTokenSource)
{
if (!this.taskFinished)
{
cancellationTokenSource?.Cancel();
throw new NoInternetException();
}
}
protected async Task RunTaskFuncWrappedAsync(Func<Task> taskFunc)
{
await taskFunc.Invoke();
this.taskFinished = true;
}
protected async Task<T> RunTaskFuncWrappedAsync<T>(Func<Task<T>> taskFunc)
{
var result = await taskFunc.Invoke();
this.taskFinished = true;
return result;
}
}
然后你可以这样称呼它:
await new TaskWithTimeoutWrapper().RunWithCustomTimeoutAsync(10000, () => this.MyTask());
或者
var myResult = await new TaskWithTimeoutWrapper().RunWithCustomTimeoutAsync(10000, () => this.MyTaskThatReturnsMyResult());
如果您想在超时时取消正在运行的异步任务,您可以添加一个取消令牌。
希望能帮助到你
我喜欢做的另一种方式:
public class TimeoutAction
{
private Thread ActionThread { get; set; }
private Thread TimeoutThread { get; set; }
private AutoResetEvent ThreadSynchronizer { get; set; }
private bool _success;
private bool _timout;
/// <summary>
///
/// </summary>
/// <param name="waitLimit">in ms</param>
/// <param name="action">delegate action</param>
public TimeoutAction(int waitLimit, Action action)
{
ThreadSynchronizer = new AutoResetEvent(false);
ActionThread = new Thread(new ThreadStart(delegate
{
action.Invoke();
if (_timout) return;
_timout = true;
_success = true;
ThreadSynchronizer.Set();
}));
TimeoutThread = new Thread(new ThreadStart(delegate
{
Thread.Sleep(waitLimit);
if (_success) return;
_timout = true;
_success = false;
ThreadSynchronizer.Set();
}));
}
/// <summary>
/// If the action takes longer than the wait limit, this will throw a TimeoutException
/// </summary>
public void Start()
{
ActionThread.Start();
TimeoutThread.Start();
ThreadSynchronizer.WaitOne();
if (!_success)
{
throw new TimeoutException();
}
ThreadSynchronizer.Close();
}
}
CancellationTokenSource cts = new CancellationTokenSource();
cts.CancelAfter(10000);
try
{
Task task = Task.Run(() => { methodToTimeoutAfter10Seconds(); }, cts.Token);
TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
using (cts.Token.Register(s => ((TaskCompletionSource<bool>)s).TrySetResult(true), tcs))
{
if (task != await Task.WhenAny(task, tcs.Task))
{
throw new OperationCanceledException(cts.Token);
}
}
/* Wait until the task is finish or timeout. */
task.Wait();
/* Rest of the code goes here */
}
catch (TaskCanceledException)
{
Console.WriteLine("Timeout");
}
catch (OperationCanceledException)
{
Console.WriteLine("Timeout");
}
catch (Exception ex)
{
Console.WriteLine("Other exceptions");
}
finally
{
cts.Dispose();
}