Feature Request: Add ElseDo and ElseDoAsync

[b564518128]

Would really appreciate to see ElseDo and ElseDoAsync get added to the toolkit. The relationship between ElseDo and Else would be similar to that between ThenDo and Then. The best use case for ElseDo would be emitting a log when error happened but still want to carry over the error status.

example usecase:

2.ToErrorOr()
  .FailIf(val => val == 2, Error.Unexpected())
  .ThenDo(val => Console.Writeline("value is not 2")
  .ElseDo(_ => Console.Writeline("value is 2 :(")

[cottozen]

Some time ago I had the same need and added this feature In PR #117

[zbyszekprasak]

In case like this I suggest using below solution, works against 2.0.1 version:

2.ToErrorOr()
    .FailIf(val => val == 2, Error.Unexpected())
    .Switch(
        val => Console.WriteLine("value is not 2"),
        _ => Console.WriteLine("value is 2 :("));

[cottozen]

Right, but at times you only want to log something on error states. You could use the Else method but that takes a Func (instead of an Action) as its argument making the code a bit ugly in my opinion.

2.ToErrorOr()
    .FailIf(val => val == 2, Error.Unexpected())
    .Else(errors => {
        Console.WriteLine("value is 2 :(");
        return errors;
    });

compared to the ElseDo implementation.

2.ToErrorOr()
    .FailIf(val => val == 2, Error.Unexpected())
    .ElseDo(_ => Console.WriteLine("value is 2 :("));

[zbyszekprasak]

@cottozen I fully agree. My remark regards the original example posted by @b564518128 .

[b564518128]

@zbyszekprasak Thanks for the response, my need is exactly what @cottozen has described though.

[b564518128]

@zbyszekprasak Another issue with using Switch is that it returns void, which means it has to be the last step of the chain. However, logging needs do not only occur at the end of the chain. ElseDo can keep the chain going.