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i think you can do it with Apply instead of async/await - something like
```InputList&lt;string&gt; acceptedProtocols = ...

InputList&lt;Union&lt;string, FrontDoorProtocol&gt;&gt; protocols = acceptedProtocols.Apply(list =&gt;
   list.Select(x =&gt; buildUnion(x, ...));```

Thank you <@U01QFM8E9A9> I think this will work. I completely missed the fact that  has a `Union.From()` factory method

```AcceptedProtocols = rule.AcceptedProtocols.Apply(protocolArray =&gt; protocolArray.Select(Union&lt;string, FrontDoorProtocol&gt;.FromT1))```
Just for completeness in case someone else looks that thread.