Question

在字符串比较中有C＃开关的要求。

string result = getResponse();
switch (result)
{
    case "S0": ret = "true";
               break;
    case "S1": ret = "fail";
               break;
    // ? can be any digit number, ex, M:0, M:100, M:1000
    case "M:?": ret = result;
               break;                 
    default: ret = "wrong";
               break;
}

如何在“M：？”中创建switch语句情况？

Answer 1

如果您使用的是C＃7，则可以使用switch pattern matching.

string ret = string.Empty;
string result = getResponse();
switch (result)
{
    case "S0":
        ret = "true";
        break;
    case "S1":
        ret = "fail";
        break;
    case var val when new Regex(@"^M:\d+").IsMatch(val):
        ret = val;
        break;
    default:
        ret = "wrong";
        break;
}

正如@KingKing在问题中评论说许多开发人员没有使用C＃7的奢侈品，那时你可以使用以下代码：

string result = getResponse();
switch (Regex.IsMatch(result, @"^M:\d+") ? "M:XXX" : result)
{
        case "S0":
            ret = "true";
            break;
        case "S1":
            ret = "fail";
            break;
        case "M:XXX": // make it unique so that it will not collide with other case statement and update this value in ternary condition accordingly
            ret = result;
            break;
        default:
            ret = "wrong";
            break;
}

Answer 2

尝试使用模式匹配： -

        public string Convert(string result)
        {
            switch (result)
            {
                case "S0": return "true";
                case "S1": return "fail";
                case var m when Regex.IsMatch(m, @"^M:\d+$"): return m;
                default: return "wrong";
            }
        }

如果您使用较旧的C＃而没有模式匹配，请将您的子句移到开关

之前

        public string Convert(string result)
        {
            if(Regex.IsMatch(result, @"^M:\d+$")) return result;
            switch (result)
            {
                case "S0": return "true";
                case "S1": return "fail";
                default: return "wrong";
            }

Answer 3

另一种选择，而不是使用开关模式匹配，是使用if语句处理默认块中更复杂的情况

string ret = string.Empty;
string result = getResponse();
switch (result)
{
    case "S0":
        ret = "true";
        break;
    case "S1":
        ret = "fail";
        break;
    default:
        Regex rgx = new Regex(@"^M:\d+");
        if (rgx.IsMatch(result))
        {
            ret = result;
        }
        else {
            ret = "wrong";
        }
        break;
}

Answer 4

如何使用LINQ：

var switches = new Func<string, string>[]
{
    x => x == "S0" ? "true" : null,
    x => x == "S1" ? "fail" : null,
    x =>
    {
        var match = Regex.Match(x, @"^M:(\d+)");
        if (match.Success)
            return match.Groups[1].Captures[0].Value;
        return null;
    },
    x => "wrong",
};

string result = "M:47";
string ret = switches.Select(s => s(result)).Where(r => r != null).First();

这为"47"提供了ret。

交换机中的多字符串比较

4 个答案: