Async, Await 是基于 .NEt 4.5架构的， 用于处理异步，防止死锁的方法的开始和结束, 提高程序的响应能力。比如：
Application area Supporting APIs that contain async methods
Web access HttpClient , SyndicationClient
Working with files StorageFile, StreamWriter, StreamReader, XmlReader
Working with images MediaCapture, BitmapEncoder, BitmapDecoder
WCF programming Synchronous and Asynchronous Operations
Async, Await 不会产生新的线程。 但是Task.Run 方法就是多线程的。 Asynchronous code is code that returns upon completion. By Task.Run, we can make is a multithreaded.
Take files as an example I encountered today:
public async Task SendFallMail(string path){ try { mail.Subject = subjectFall; mail.Body = "Fall down!"; using (MailMessage ms = mail) { ms.Attachments.Add(new Attachment(path)); using (SmtpClient sc = SmtpServer) { Task t = Task.Factory.StartNew(() => { sc.Send(ms); }); await t; } } File.Delete(path); } catch (Exception ex) { MessageBox.Show(ex.ToString()); }
It should wait t which is sending an e-mail wihich attached an picture in path.
Then delete the pic in path, wihch is working properly after I use the using statement...
Without using the using statement, it shows IO exception said:
C# Async, Await and using statements
原文：http://www.cnblogs.com/bruceyo/p/4026522.html