Should we use CancellationToken with MVC/Web API controllers?

Question

There are different examples for async controllers. Some of them use CancellationToken in method definition:

public async Task<ActionResult> ShowItem(int id, CancellationToken cancellationToken) {     await Database.GetItem(id, cancellationToken);     ... 

But other examples and even the default ASP.NET projects for VS2013 don't use CancellationToken at all and work without it:

public async Task<ActionResult> ShowItem(int id) {     await Database.GetItem(id);     ... 

It's not clear, if we should use CancellationToken in controllers or not (and why).

Answer 1

You should use it. Right now it only applies if you have an AsyncTimeout, but it's likely that a future MVC/WebAPI version will interpret the token as "either timeout or the client disconnected".

Answer 2

You could use this

public async Task<ActionResult> MyReallySlowReport(CancellationToken cancellationToken) {     CancellationToken disconnectedToken = Response.ClientDisconnectedToken;     using (var source = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, disconnectedToken))     {         IEnumerable<ReportItem> items;         using (ApplicationDbContext context = new ApplicationDbContext())         {             items = await context.ReportItems.ToArrayAsync(source.Token);         }         return View(items);     } } 

taken from here.