Type test pattern with array

Question

I have a situation where I am handed an object and need to produce a string. In most cases, I can just call `.ToString()` and be done with it (works for strings, numbers, dates, etc.) One situation where this doesn't work is a byte array representing a GUID. In that case, `ToString()` simply reports "System.Byte[]". I am trying to use pattern matching to catch byte arrays so that I can customize the string-ification. But I can't figure out how to match a byte array (or, really, any array) except via the Array pattern. A GUID is 16 bytes long, and I really don't want to have a pattern with 16 named array elements. Also, using the array pattern causes F# to want an array as the input, rather than an object: ``` match value (* <-- obj *) with | [| b1; b2; b3; b4; b5; b6; b7; b8; b9; b10; b11; b12; b13; b14; b15; b16 |] -> (* do some magic here later... *) b1.ToString() | x -> x.ToString() ``` ``` > This expression was expected to have type obj but here has type 'a [] ``` I tried to use T…

Accepted Answer

You can use:

```
match o with
| :? array<byte> as guid -> ...
```

You can also put brackets around the type name:

```
 match o with
    | :? (byte[]) as guid -> ...
```

or

```
 match o with
    | :? (byte array) as guid -> ...
```

Type test pattern with array

Solution

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