Async/Await exception handling

Async/Await exception handling

My question is based on article Best Practices in Asynchronous Programming
So i have this code
async static void AsyncVersion()
{
Stopwatch sw = Stopwatch.StartNew();
string url1 = "http://rsdn.ru";
string url2 = "http://gotdotnet.ru";
string url3 = "http://blogs.msdn.com";
var webRequest1 = WebRequest.Create(url1);
Console.WriteLine("Before webRequest1.GetResponseAsync(). Thread
Id: {0}",
Thread.CurrentThread.ManagedThreadId);
...
so this code throws exception, for example when i haven't inet connection.
So when i'm following msdn's guidances and change signature of method to
Task (instead of void), but after this it devour all exceptions, but hey
aren't handle by external catch block.
Entire code is below
using System;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApplication8
{
class Program
{
async static Task AsyncVersion()
{
Stopwatch sw = Stopwatch.StartNew();
string url1 = "http://rsdn.ru";
string url2 = "http://gotdotnet.ru";
string url3 = "http://blogs.msdn.com";
var webRequest1 = WebRequest.Create(url1);
Console.WriteLine("Before webRequest1.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse1 = await webRequest1.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url1,
webResponse1.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
var webRequest2 = WebRequest.Create(url2);
Console.WriteLine("Before webRequest2.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse2 = await webRequest2.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url2,
webResponse2.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
var webRequest3 = WebRequest.Create(url3);
Console.WriteLine("Before webRequest3.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse3 = await webRequest3.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url3,
webResponse3.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
}
static void Main(string[] args)
{
try
{
Console.WriteLine("Main thread id: {0}",
Thread.CurrentThread.ManagedThreadId);
Task task = new Task(() => AsyncVersion());
task.Start();
Console.WriteLine("Right after AsyncVersion() method call");
//Îæèäàåì çàâåðøåíèÿ àñèíõðîííîé îïåðàöèè
task.Wait();
Console.WriteLine("Asyncronous task finished!");
}
catch (Exception e)
{
//Âñå èñêëþ÷åíèÿ â TPL ïðîáðàñûâàþòñÿ îáåðíóòûå â
AggregateException
Console.WriteLine("Exceptopn: {0}", e.Message);
}
Console.ReadLine();
}
}
}
old version:
using System;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApplication8
{
class Program
{
async static void AsyncVersion()
{
Stopwatch sw = Stopwatch.StartNew();
string url1 = "http://rsdn.ru";
string url2 = "http://gotdotnet.ru";
string url3 = "http://blogs.msdn.com";
var webRequest1 = WebRequest.Create(url1);
Console.WriteLine("Before webRequest1.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse1 = await webRequest1.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url1,
webResponse1.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
var webRequest2 = WebRequest.Create(url2);
Console.WriteLine("Before webRequest2.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse2 = await webRequest2.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url2,
webResponse2.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
var webRequest3 = WebRequest.Create(url3);
Console.WriteLine("Before webRequest3.GetResponseAsync().
Thread Id: {0}",
Thread.CurrentThread.ManagedThreadId);
var webResponse3 = await webRequest3.GetResponseAsync();
Console.WriteLine("{0} : {1}, elapsed {2}ms. Thread Id: {3}",
url3,
webResponse3.ContentLength, sw.ElapsedMilliseconds,
Thread.CurrentThread.ManagedThreadId);
}
static void Main(string[] args)
{
try
{
Console.WriteLine("Main thread id: {0}",
Thread.CurrentThread.ManagedThreadId);
Task task = new Task(AsyncVersion);
task.Start();
Console.WriteLine("Right after AsyncVersion() method call");
//Îæèäàåì çàâåðøåíèÿ àñèíõðîííîé îïåðàöèè
task.Wait();
Console.WriteLine("Asyncronous task finished!");
}
catch (System.AggregateException e)
{
//Âñå èñêëþ÷åíèÿ â TPL ïðîáðàñûâàþòñÿ îáåðíóòûå â
AggregateException
Console.WriteLine("AggregateException: {0}",
e.InnerException.Message);
}
Console.ReadLine();
}
}
}