Is there a way to figure out in ASP.NET Web API beta whether the HTTP request was cancelled (aborted by user of for any another reason)? I'm looking for opportunity to have a kind of cancellation token out-of-the-box that will signal that the request is aborted and therefore long-running ops should be aborted as well.
Possible related question - the use case for the CancellationTokenModelBinder class. What's the reason to have a separate binder for cancellation token?
You could check Response.IsClientConnected from time to time to see if the browser is still connected to the server.
I'd like to sum-up a bit. The only approach that seem to work is checking Response.IsClientConnected. Here some technical details regarding what is going behind the stage: here and here This approach has some flaws:
At the end I came up with the following piece of code to inject CancellationToken based on IsClientConnected into the Web API controller:
public class ConnectionAbortTokenAttribute : System.Web.Http.Filters.ActionFilterAttribute
{
private readonly string _paramName;
private Timer _timer;
private CancellationTokenSource _tokenSource;
private CancellationToken _token;
public ConnectionAbortTokenAttribute(string paramName)
{
_paramName = paramName;
}
public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
{
object value;
if (!actionContext.ActionArguments.TryGetValue(_paramName, out value))
{
// no args with defined name found
base.OnActionExecuting(actionContext);
return;
}
var context = HttpContext.Current;
if (context == null)
{
// consider the self-hosting case (?)
base.OnActionExecuting(actionContext);
return;
}
_tokenSource = new CancellationTokenSource();
_token = _tokenSource.Token;
// inject
actionContext.ActionArguments[_paramName] = _token;
// stop timer on client disconnect
_token.Register(() => _timer.Dispose());
_timer = new Timer
(
state =>
{
if (!context.Response.IsClientConnected)
{
_tokenSource.Cancel();
}
}, null, 0, 1000 // check each second. Opts: make configurable; increase/decrease.
);
base.OnActionExecuting(actionContext);
}
/*
* Is this guaranteed to be called?
*
*
*/
public override void OnActionExecuted(System.Web.Http.Filters.HttpActionExecutedContext actionExecutedContext)
{
if(_timer != null)
_timer.Dispose();
if(_tokenSource != null)
_tokenSource.Dispose();
base.OnActionExecuted(actionExecutedContext);
}
}
If you added CancellationToken in to controller methods, it will be automatically injected by the framework, and when a client calls xhr.abort() the token will be automatically cancelled
Something similar to
public Task<string> Get(CancellationToken cancellationToken = default(CancellationToken))
For MVC you can also refer to
HttpContext.Current.Response.IsClientConnected
HttpContext.Response.ClientDisconnectedToken
For .NetCore
services.AddTransient<ICustomInterface>(provider => {
var accessor = provider.GetService<IHttpContextAccessor>);
accessor.HttpContext.RequestAborted;
});
