Asynchronous Programming
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The document discusses asynchronous programming with C# async and await keywords. It covers how async methods are non-blocking and return control to the caller immediately. The anatomy of async methods requires the method be marked async and calls within can be awaited. Async methods can return void, Task or Task<T> depending on needs. The document demonstrates how to handle exceptions, cancellations, report progress, and await methods sequentially or in parallel using Task.WhenAll/WhenAny.
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Asynchronous Programming
- 1. Asynchronous Programming Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 2. Asynchronous Programming http:// www.LearnNowOnline.com Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 3. Understanding the Problem with Previous Async Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 4. Understanding the Problem with Previous Async • Demo Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 5. Where Async Fits In Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 6. Where Async Fits In • Traditional code is synchronous Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 7. Where Async Fits In • Traditional code is synchronous • Call method, block until call returns, continue processing Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 8. Where Async Fits In • Traditional code is synchronous • Call method, block until call returns, continue processing • Asynchronous (async) is non-blocking Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 9. Where Async Fits In • Traditional code is synchronous • Call method, block until call returns, continue processing • Asynchronous (async) is non-blocking • Call, return immediately to continue processing, called method continues running Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 10. Where Async Fits In • Traditional code is synchronous • Call method, block until call returns, continue processing • Asynchronous (async) is non-blocking • Call, return immediately to continue processing, called method continues running • UI is responsive and good use of server Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 11. Previous Async Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 12. Previous Async • Asynchronous Programming Model (APM) Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 13. Previous Async • Asynchronous Programming Model (APM) • Relies on delegates to handle execution and callback Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 14. Previous Async • Asynchronous Programming Model (APM) • Relies on delegates to handle execution and callback • Complex Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 15. Previous Async • Asynchronous Programming Model (APM) • Relies on delegates to handle execution and callback • Complex • Event-based Asynchronous Pattern (EAP) Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 16. Previous Async • Asynchronous Programming Model (APM) • Relies on delegates to handle execution and callback • Complex • Event-based Asynchronous Pattern (EAP) • Simpler and more features than APM Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 17. Using the New async and await Keywords Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 18. Using the New async and await Keywords • Demo Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 19. Anatomy of an Async Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 20. Anatomy of an Async • Modify method as async (required) Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 21. Anatomy of an Async • Modify method as async (required) • Call method with await (optional) Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 22. Anatomy of an Async • Modify method as async (required) • Call method with await (optional) • Without await: generates compiler warning and method runs synchronously Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 23. Anatomy of an Async • Modify method as async (required) • Call method with await (optional) • Without await: generates compiler warning and method runs synchronously • Method, lambda, or anonymous method Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 24. Anatomy of an Async • Modify method as async (required) • Call method with await (optional) • Without await: generates compiler warning and method runs synchronously • Method, lambda, or anonymous method • Add Async suffix to method name Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 25. Async Return Values Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 26. Async Return Values • Can be void, Task, or Task<TResult> Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 27. Async Return Values • Can be void, Task, or Task<TResult> • Use void for fire-and-forget Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 28. Async Return Values • Can be void, Task, or Task<TResult> • Use void for fire-and-forget • Warning: can’t catch exception with void Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 29. Async Return Values • Can be void, Task, or Task<TResult> • Use void for fire-and-forget • Warning: can’t catch exception with void • Appropriate for async event handlers Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 30. Async Return Values • Can be void, Task, or Task<TResult> • Use void for fire-and-forget • Warning: can’t catch exception with void • Appropriate for async event handlers • Task and Task<TResult> lets callers await your method Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 31. Async Return Values • Can be void, Task, or Task<TResult> • Use void for fire-and-forget • Warning: can’t catch exception with void • Appropriate for async event handlers • Task and Task<TResult> lets callers await your method • Assign awaited value to variable and continue with rest of method Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 32. Managing Async Tasks Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 33. Managing Async Tasks • Demo Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 34. About Async Threads Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 35. About Async Threads • Call to await returns to caller on same thread Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 36. About Async Threads • Call to await returns to caller on same thread • Control automatically marshaled back to UI thread after await Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 37. Awaiting in Sequence Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 38. Awaiting in Sequence • You can have as many awaits in a method that you want Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 39. Awaiting in Sequence • You can have as many awaits in a method that you want • After one await completes, the next one executes Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 40. Awaiting in Parallel Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 41. Awaiting in Parallel • You can await multiple methods together Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 42. Awaiting in Parallel • You can await multiple methods together • Add all methods to List<Task<TResult>> Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 43. Awaiting in Parallel • You can await multiple methods together • Add all methods to List<Task<TResult>> • Call await on Task.WhenAll to process results after all tasks complete Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 44. Awaiting in Parallel • You can await multiple methods together • Add all methods to List<Task<TResult>> • Call await on Task.WhenAll to process results after all tasks complete • Call await on Task.WhenAny to process results for each result as it completes Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 45. Exceptions, Cancellations, and Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 46. Exceptions, Cancellations, and • Demo Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 47. Handling Exceptions Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 48. Handling Exceptions • You can handle both synchronous and async code together Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 49. Handling Exceptions • You can handle both synchronous and async code together • Use try/catch around await and it works Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 50. Cancellation Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 51. Cancellation • Use CancellationTokenSource Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 52. Cancellation • Use CancellationTokenSource • Pass Token to async methods Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 53. Cancellation • Use CancellationTokenSource • Pass Token to async methods • Wrap in try/catch for OperationCancelledException Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 54. Cancellation • Use CancellationTokenSource • Pass Token to async methods • Wrap in try/catch for OperationCancelledException • Awaited code can check token for cancellation and throw Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 55. Progress Reporting Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 56. Progress Reporting • Modify async method to accept an IProgress<T> Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 57. Progress Reporting • Modify async method to accept an IProgress<T> • Caller instantiates ProgressReport with callback Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 58. Progress Reporting • Modify async method to accept an IProgress<T> • Caller instantiates ProgressReport with callback • Caller passes the ProgressReport instance to the async method Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 59. Progress Reporting • Modify async method to accept an IProgress<T> • Caller instantiates ProgressReport with callback • Caller passes the ProgressReport instance to the async method • The async method calls Report on IProgress<T> instance Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 60. Questions? Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
- 61. Questions? http:// www.LearnNowOnline.com Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company
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