Making interface implementations async

Question

I   m currently trying to make my application using some Async methods  All my IO is done through explicit implementations of an interface and I am a bit confused about how to make the operations async   As I see things I have two options in the implementation   interface IIO       void DoOperation        OPTION1  Do an implicit implementation async and await the result in the implicit implementation   class IOImplementation   IIO         async void DoOperation                 await Task Factory StartNew      gt                                  WRITING A FILE OR SOME SUCH THINGAMAGIG                             region IIO Members      void IIO DoOperation                 DoOperation                endregion     OPTION2  Do the explicit implementation async and await the task from the implicit implementation   class IOAsyncImplementation   IIO       private Task DoOperationAsync                 return new Task      gt                                  DO ALL THE HEAVY LIFTING                                region IIOAsync Members      async void IIO DoOperation                 await DoOperationAsync                endregion     Are one of these implementations better than the other or is there another way to go that I am not thinking of

User · Answer

An abstract class can be used instead of an interface  in C  7 3      Like interface abstract class IIO       public virtual async Task lt string gt  DoOperation string Name                throw new NotImplementedException       throwing exception            return await Task Run      gt    return  quot  quot          or empty do             Implementation class IOImplementation   IIO       public override async Task lt string gt  DoOperation string Name                return await await Task Run      gt                        if Name     quot Spiderman quot                   return  quot ok quot               return  quot cancel quot

User · Answer

Neither of these options is correct  You re trying to implement a synchronous interface asynchronously  Don t do that  The problem is that when DoOperation   returns  the operation won t be complete yet  Worse  if an exception happens during the operation  which is very common with IO operations   the user won t have a chance to deal with that exception   What you need to do is to modify the interface  so that it is asynchronous   interface IIO       Task DoOperationAsync       note  no async here    class IOImplementation   IIO       public async Task DoOperationAsync                    perform the operation here           This way  the user will see that the operation is async and they will be able to await it  This also pretty much forces the users of your code to switch to async  but that s unavoidable   Also  I assume using StartNew   in your implementation is just an example  you shouldn t need that to implement asynchronous IO   And new Task   is even worse  that won t even work  because you don t Start   the Task

User · Answer

Better solution is to introduce another interface for async operations  New interface must inherit from original interface   Example    interface IIO       void DoOperation       interface IIOAsync   IIO       Task DoOperationAsync        class ClsAsync   IIOAsync       public void DoOperation                 DoOperationAsync   GetAwaiter   GetResult               public async Task DoOperationAsync                   just an async code demo         await Task Delay 1000             class Program       static void Main string   args                IIOAsync asAsync   new ClsAsync            IIO asSync   asAsync           Console WriteLine DateTime Now Second            asAsync DoOperation            Console WriteLine  After call to sync func using Async iface   0                 DateTime Now Second            asAsync DoOperationAsync   GetAwaiter   GetResult            Console WriteLine  After call to async func using Async iface   0                 DateTime Now Second            asSync DoOperation            Console WriteLine  After call to sync func using Sync iface   0                 DateTime Now Second            Console ReadKey true             P S  Redesign your async operations so they return Task instead of void  unless you really must return void

[c#] Making interface implementations async

Examples related to c#

Examples related to asynchronous

Examples related to async-await