.NET常数的F#模式匹配 [英] F# pattern matching of .Net constants

问题描述

下一个示例中的代码

open System.Drawing

let testColor c =
    match c with
    | Color.Black -> 1
    | Color.White -> 0
    | _ -> failwith "unexpected color"

不会编译.错误是Error 1 The field, constructor or member 'Black' is not defined.

如何与.Net常量或以大写字母开头的枚举进行模式匹配?

How do I pattern match against .Net constants or enums that start with capital letters?

对于它的价值，编译器是"Microsoft(R)F#2.0 Interactive build 4.0.30319.1".

For what it's worth, the compiler is "Microsoft (R) F# 2.0 Interactive build 4.0.30319.1".

推荐答案

您无法针对任意对象值进行模式匹配.使用if then else或when条件:

You can't pattern-match against arbitrary object values. Use an if then else or when conditions:

let testColor c = 
    match c with 
    | c when c = Color.Black -> 1 
    | c when c = Color.White -> 0 
    | _ -> failwith "unexpected color"

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