此 'let' 之后的块未完成，尽管从函数返回值但 F# 错误

Question

 | Log (message, ack) ->

         let CreateEventSourcingConnection() =
             task {
                 let connection =
                     let ipEndPoint = IPEndPoint(IPAddress.Loopback, 1113)
                     EventStoreConnection.Create(ipEndlPoint)
                 do! connection.ConnectAsync()
                 return connection
             }

         let AddEventToStreamAsync (connection: IEventStoreConnection) streamName eventName message =
             task {
                 let serializedEventData =
                     message
                     |> JsonConvert.SerializeObject
                     |> Encoding.UTF8.GetBytes
                 let event = EventData(Guid.NewGuid(), eventName, true, serializedEventData, null)

                 let! _ = connection.AppendToStreamAsync(streamName, int64 ExpectedVersion.Any, event)
                 ()
             }

错误：

The block following this 'let' is unfinished. Every code block is an expression and must have a result. 'let' cannot be the final code element in a block. Consider giving this block an explicit result.

我试过在定义它们之后调用这些函数。我也检查了我的缩进，我想应该没问题。我知道我需要 return 函数的值，但我想我已经这样做了。

Answer 1

我怀疑（不知道哪个 let 语句导致了错误）您需要 return 从模式匹配中获取一些东西（即 | Log (message, ack) -> 之后的部分） ).

如果你不需要 return 任何东西，你可以只 return () 最后，与两个外部 [=10= 的缩进级别相同]s，但注意模式匹配的所有分支都需要return相同的类型。

此 'let' 之后的块未完成，尽管从函数返回值但 F# 错误

The block following this 'let' is unfinished, F# error despite returning the value from function

f#

pattern-matching

let