using c#5 async for non-blocking

Question

If I have a web application that wraps calls to the network and database in a Task<T> and awaits them, this should prevent the thread from blocking so it can be re-used.

However, when the IO work is carried out, is there still some thread that is blocked, so there is no real benefit to awaiting?

Stephen Cleary · Accepted Answer · 2013-01-31 13:15:42Z

2

If you are just wrapping blocking calls in a Task.Run, then you are correct: there is no benefit.

However, if you are using naturally-asynchronous methods (e.g., asynchronous HttpClient/WebClient/HttpWebRequest methods and asynchronous database methods), then no threads are used by those requests, and you get a scalability benefit.

At the device driver level of Windows, all I/O is asynchronous. The synchronous APIs are just convenience wrappers. Naturally-asynchronous methods do not block a thread over the synchronous APIs; they are built on the asynchronous APIs.

answered Jan 31, 2013 at 13:15

Stephen Cleary

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Stephen Cleary Over a year ago

This information is scattered all over MSDN and various SDKs, but some good resources are Windows Internals and CLR via C#.

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