.net - How can I cancel Task.WhenAll? -

currenly using following code wait collection of tasks complete. however, have situation want able cancel/abort whenall call, via cancellation token preferably. how go that?

  dim taskcollection new list(of tasks.task)   x integer = 1 threads     dim newtask tasks.task = taskhandler.delegates(delegatekey).invoke(me, proxies, totalparams).continuewith(sub() threadfinished())     taskcollection.add(newtask)   next    await tasks.task.whenall(taskcollection) 

i'm assuming it's going along lines of next bit of code, i'm not sure go in 'xxx'.

await tasks.task.whenany(tasks.task.whenall(taskcollection), xxx) 

use taskcompletionsource<t> create task asynchronous condition not have asynchronous api. use cancellationtoken.register hook modern cancellationtoken-based cancellation system cancellation system. solution needs combine these two.

i have cancellationtoken.astask() extension method in asyncex library, can write own such:

<system.runtime.compilerservices.extension> _ public shared function astask(cancellationtoken cancellationtoken) task   dim tcs = new taskcompletionsource(of object)()   cancellationtoken.register(function() tcs.trysetcanceled(), usesynchronizationcontext := false)   return tcs.task end function 

usage expected:

await task.whenany(task.whenall(taskcollection), cancellationtoken.astask())