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

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.

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

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

[c#] Making interface implementations async

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