在F＃匹配语句如何匹配的类型byte []？ [英] in f# match statement how do I match to the type byte[]?

问题描述

我想从.NET类型查找的DbType枚举值。我使用的是匹配语句。不过，我无法弄清楚如何匹配的类型byte []。

I'm trying to lookup DbType enumeration values from .net types. I'm using a match statement. However I cannot figure out how to match on the type byte[].

let dbType x =
  match x with
  | :? Int64 -> DbType.Int64
  | :? Byte[] -> DbType.Binary // this gives an error
  | _ -> DbType.Object

如果有更好的方法来映射这些类型的，我会接受的建议。

If there is a better way to map these types, I would be open to suggestions.

推荐答案

字节[] ，字节数组，和阵列和LT;字节＆GT; 都是同义的，但在这种情况下只有最后将工作没有括号：

byte[], byte array, and array<byte> are all synonymous, but in this context only the last will work without parentheses:

let dbType (x:obj) =
    match x with
    | :? (byte[])     -> DbType.Binary
    | :? (byte array) -> DbType.Binary // equivalent to above
    | :? array<byte>  -> DbType.Binary // equivalent to above
    | :? int64        -> DbType.Int64
    | _               -> DbType.Object

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