c#中的多线程异常

1.对于Thread操作的异常处理

public static void Main()
{
try
{

　　Thread th = new Thread(DoWork);
th.Start();
}
catch (Exception ex)
{
// Non-reachable code
Console.WriteLine ("Exception!");
}
}
static void DoWork()

{

　　……

　　 throw null;　　// Throws a NullReferenceException

}

在DoWork函数里抛出的异常时不会被主线程的try,catch捕捉的，各个线程应该有自己的try,catch去处理线程异常。

正确写法：

public static void Main()
{
Thread th = new Thread(DoWork);
th.Start();
}
static void DoWork()
{
try
{
……
throw null; // The NullReferenceException will be caught below
}
catch (Exception ex)
{
Typically log the exception, and/or signal another thread
that we've come unstuck
...
}

}

2. 异步函数的异常处理

例如如 WebClient中的 UploadStringAsync,它的异常会在UploadStringCompleted的参数error里

static void Main(string[] args)
{
WebClient webClient = new WebClient();
webClient.UploadStringCompleted += new UploadStringCompletedEventHandler((sender, e) =>
{
if (e.Error != null)
{
Console.WriteLine(e.Error.Message);
}
});
webClient.UploadStringAsync(new Uri("http://www.baidu.com"), "1111");
Console.ReadKey();
}

3 Task的异常处理

把try包含task.wait()函数，就能捕捉task的异常

Task task = Task.Run (() => { throw null; });
try
{
task.Wait();
}
catch (AggregateException aex)
{
if (aex.InnerException is NullReferenceException)
Console.WriteLine ("Null!");
else
throw;
}

或者 在continue函数里处理TaskContinuationOptions.OnlyOnFaulted的状态

Task<List<int>> taskWithFactoryAndState =
Task.Factory.StartNew<List<int>>((stateObj) =>
{
List<int> ints = new List<int>();
for (int i = 0; i < (int)stateObj; i++)
{
ints.Add(i);
if (i > 100)
{
InvalidOperationException ex =
new InvalidOperationException("oh no its > 100");
ex.Source = "taskWithFactoryAndState";
throw ex;
}
}
return ints;
}, 2000);

//and setup a continuation for it only on when faulted
taskWithFactoryAndState.ContinueWith((ant) =>
{
AggregateException aggEx = ant.Exception;
Console.WriteLine("OOOOPS : The Task exited with Exception(s)");
　　 foreach (Exception ex in aggEx.InnerExceptions)
{
Console.WriteLine(string.Format("Caught exception '{0}'",
ex.Message));
}
}, TaskContinuationOptions.OnlyOnFaulted);

//and setup a continuation for it only on ran to completion
taskWithFactoryAndState.ContinueWith((ant) =>
{
List<int> result = ant.Result;
foreach (int resultValue in result)
{
Console.WriteLine("Task produced {0}", resultValue);
}
}, TaskContinuationOptions.OnlyOnRanToCompletion);
Console.ReadLine();

4 c# 5.0 中的async ,await 异常捕捉

static async Task ThrowAfter(int timeout, Exception ex)
{
　　await Task.Delay(timeout);
　　throw ex;
}

static async Task MissHandling()
{
　　var t1 = ThrowAfter(1000, new NotSupportedException("Error 1"));

　　try
　　{
　　　　await t1;
　　}
　　catch (NotSupportedException ex)
　　{
　　　　Console.WriteLine(ex.Message);
　　}
}