Asynchronous Programming

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Asynchronous Programming

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