Skip to main content

C#–Handling cancellation requests

When creating an async method in C#, I typically add the option to pass a CancellationToken. That is the easy part. But what if a consumer of your method uses this CancellationToken to request a cancellation? What is the proper way to cancel your code? Let's find out...

In most cases, it will be sufficient to pass the cancellation token to a lower-level API, but if we are providing the lowest-level API it is up to us to correctly handle the cancellation request.

The correct way to handle cancellations is by throwing an OperationCanceledException when a cancellation is requested.

To help you with this, a convenient ThrowIfCancellationRequested() method exists on the CancellationToken object.

Here are some other considerations to take into account when implementing cancellation:

  • Don’t cancel if you operation incures side-effects that would leave the system in an inconsistent state.
  • Don’t throw an OperationCancelledException when the work has already completed.
  • Start by checking if a cancellation was requested before executing your logic.
  • For work that is executed very quick, it it an option to not check the token(although calling CancellationToken.ThrowIfCancellationRequested() is pretty lightweight)
  • Check CancellationToken.CanBeCanceled when you can do your work more efficiently if you can assume you’ll never be canceled.

Popular posts from this blog

XUnit - Assert.Collection

A colleague asked me to take a look at the following code inside a test project: My first guess would be that this code checks that the specified condition(the contains) is true for every element in the list.  This turns out not to be the case. The Assert.Collection expects a list of element inspectors, one for every item in the list. The first inspector is used to check the first item, the second inspector the second item and so on. The number of inspectors should match the number of elements in the list. An example: The behavior I expected could be achieved using the Assert.All method:

Angular --deploy-url and --base-href

As long you are running your Angular application at a root URL (e.g. ) you don’t need to worry that much about either the ‘--deploy-url’ and ‘--base-href’ parameters. But once you want to serve your Angular application from a server sub folder(e.g. ) these parameters become important. --base-href If you deploy your Angular app to a subfolder, the ‘--base-href’ is important to generate the correct routes. This parameter will update the <base href> tag inside the index.html. For example, if the index.html is on the server at /angularapp/index.html , the base href should be set to <base href="/angularapp/"> . More information: --deploy-url A second parameter that is important is ‘--deploy-url’. This parameter will update the generated url’s for our assets(scripts, css) inside the index.html. To make your assets available at /angularapp/, the deploy url should

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.