20131004_Async await - howard

1. Async Await
Howard 2013/10/04

2. Async Methods Are Easier toWrite
• The Async and Await keywords inVisual Basic and the async and await
keywords in C# are the heart of async programming. By using those two
keywords, you can use resources in the .NET Framework or theWindows
Runtime to create an asynchronous method almost as easily as you create a
synchronous method. Asynchronous methods that you define by using
async and await are referred to as async methods.

3. Async Methods Are Easier toWrite
• The following characteristics summarize what makes the previous example an
async method.
• The method signature includes an Async or async modifier.
• The name of an async method, by convention, ends with an "Async" suffix.
• The return type is one of the following types:
• Task<TResult> if your method has a return statement in which the operand has typeTResult.
• Task if your method has no return statement or has a return statement with no operand.
• Void (a Sub inVisual Basic) if you're writing an async event handler.
• The method usually includes at least one await expression, which marks a point where the
method can't continue until the awaited asynchronous operation is complete.

4. Async Await –
WebClient sample

5. What Happens in an Async Method
•

6. Thread

7. Thread
• 開啟Thread 的地方，也很難從呼叫的方法取得回傳值

8. Task

9. Async Await

10. References
• http://msdn.microsoft.com/zh-
tw/library/hh191443.aspx#BKMK_WhatHappensUnderstandinganAsyncMe
thod
• http://msdn.microsoft.com/en-us/library/vstudio/hh191443.aspx
• http://studyhost.blogspot.tw/2012/06/metro-style-appnet-45.html