Asynchronous Programming in C# - Part 1

Presenter: Vikash Kumar, Mindfire Solutions (28/07/2014)

About MeMCTS-70-515 - Microsoft .NET 4.0, Web App Development

MCP:70-483: MS - Programming in C#

Skills: MVC, Asp.Net WebForms, C#, EntityFramework, OpenAccess, TypeScript, SEO, jQuery, KendoUI, Lucene.Net, Asynchronous programming, Sql Server.

Connect Me:Blog :- http://vikutech.blogspot.in/Twitter :- https://twitter.com/viku85LinkedIn :- http://www.linkedin.com/pub/vikash-kumar/11/4b5/625Google+ :- https://plus.google.com/108754146104237310375

Contact Me:Email :- vikashk@mindfiresolutions.com / viku85@gmail.comSkype :- mfsi_vikash

Agenda What is asynchronous? Asynchronous programming options and history

Thread and ThreadPool Asynchronous Programming Model (APM) Event-based Asynchronous Pattern (EAP) Task– Basics– Exception handling– Relationships

What is asynchronous?

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To do more than one thing at a time.asyn = not with chronos = time

Asynchronous programming options and history Thread Asynchronous Programming Model (APM) Event-Based Asynchronous Pattern (EAP) BackgroundWorker Task Task Parallel Library - DataFlow Task Parallel Library – Parallel APIs Thread → APM → EAP → TAP

Thread and ThreadPool Basic building block for async programming. Parameterize thread, came with .NET 2.0

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APM and EAP APM depends upon Begin and End

methods. Callbacks are dependent on IAsyncResult. EAP came with .NET 2.0 which automatically

handles synchronization context. BackgroundWorker is an example of EAP

based programming. EAP can be seen while adding web

reference which automatically creates with proxies classes.

APM and EAP

Task A task is an abstraction of unit of work to

run asynchronously. Ways to execute: new Task(Speak).Start(),

Task.Factory.StartNew(Speak), Task.Run(Speak)

Use FromAsync when an API has BeginXXX/EndXXX.

Task can be canceled through CancellationToken and checked with ThrowIfCancellationRequested.

IProgress<T> came with 4.5 which can be used to show status

Task error handling Task are completed with following state:

Ran to Completion, Canceled and Faulted. Task uses AggregateException to wrap up

any other exception occurs which can be found under inner exception.

AggregateException comes with Flatten method to check all exceptions.

AggregateException also comes with Handle method which accepts predicate to handle errors.

ThrowUnobservedTaskExceptions to configure to shallow exception.

Cancellation

FromAsync

Progress bar

Exception handling

Task Relationships

Task

Task Task Task

Child Tasks

Task Task Task

Chained Task

Task Relationships... ContinueWhenXXX can be used to chain

up tasks with TaskContinuationOptions enum for various conditions.

TaskCreationOptions.AttachedToParent is used to create child tasks.

Creating child task will reflect exception in parent task if exception occurs.

Task.Run uses TaskCreationOptions.DenyChildAttach by default which will act as nested task.

Task Relationship

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Question and Answer

References Pro Asynchronous Programming with .NET Asynchronous Programming Patterns Asynchronous Programming in .NET: I'll Call

You Back (For definition)

Presenter: Vikash Kumar, Mindfire Solutions

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