1. www.dotnet.lv

2. Valdis Iljuconoks
Technical Fellow, Software Architect
Microsoft MVP
Geta AS, Viiar Consulting
valdis.iljuconoks@dotnet.lv
http://dotnet.lv/blogs/vi
@tech_fellow

3. C#

4. 5.0

5. Async

6. concurrency
&
asynchrony

7. sequential
concurrent
parallel
asynchronous

8. agenda
predecessors
awaiting tasks

9. predecessors

10. Asynchronous Programming Model (APM)
Event-based Asynchronous Pattern (EAP)

11. C# 5.0
C# 4.0
Async
C# 3.0 Dynamics
Language
C# 2.0 Integrated
Generics Query
C# 1.0
Component
on a
Managed
Runtime

12. awaiting tasks

13. ‘Task’ is representation of ongoing work

14. var
var

15. async / await

16. similar to synchronous code

17. referred as async method

18. modifier (async) applied to
• a method
• a lambda expression
• an anonymous method

19. keyword (await) used in
• body of an immediately enclosing method
• lambda expression
• anonymous method

20. await NOT used in
• synchronous function
• query expression
• catch or finally block
• in lock statement
• unsafe context

21. absence of an operator
cause a compiler warning

22. characteristics

23. Async methods are intended to be non-
blocking operations

24. await expression does not block the current
thread while the awaited task is running

25. expression signs up the rest of the method
as a continuation

26. and

27. returns control to the caller of the async
method.

28. Method executes synchronously
till first ‘await’.

29. Async methods don't require multithreading

30. async method doesn't run on its own thread

31. method runs on the current synchronization
context.

32. Task based async pattern

33. Async method return types
• void
• Task
• Task<TResult>

34. async void FireAndForget()
{
await t;
}
FireAndForget();

35. async Task JustSignalCompletionAsync()
{
return;
}
await JustSignalCompletionAsync();

36. async Task<int> GetResultsAsync()
{
return 5;
}
var r = await GetResultsAsync();

37. Naming conventions
• By convention, the suffix "Async" is added
• Async methods that return void are
discouraged
• Exceptions to the naming convention
(e.g. event handlers)

38. ?

39. Valdis Iljuconoks
Technical Fellow, Software Architect
Microsoft MVP
Geta AS, Viiar Consulting
valdis.iljuconoks@dotnet.lv
http://dotnet.lv/blogs/vi
@tech_fellow

40. www.dotnet.lv