Question

鉴于这些情况:

string s1 = "Abc";
string s2 = "ABC";

更快:

Regex.Match(s1, s2, RegexOptions.Ign或eCase)

或

s1.ToLower() == s2.ToLower()

If they are the same 或 the one is faster then the other, so when its better to use one over the other?

Answer 1

也许第二步比较快,但我避免这两种做法。

更好的方法是使用string.Equals 。缩略语论点:

s1.Equals(s2, StringComparison.CurrentCultureIgnoreCase)

见网站:。

Answer 2

Theoretically speaking, comparing 2 strings should be faster, RegEx are know to be rather slow.

However, if you want to match a string s1 to a RegEx s2 while ignoring case (This is not the same as comparing 2 strings), then the first solution is better as it should avoid creating another string.

与这种问题总是一样,我将有一个基准,对两个业绩进行比较:

Answer 3

@Mark Byers已经张贴了正确的答案。

我想强调,您应为never使用Tolower进行细微比较。这是不正确的。

s1.Equals(s2, StringComparison.CurrentCultureIgnoreCase) //#1
s1.ToLower() == s2.ToLower() //#2
s1.ToLowerInvariant() == s2.ToLowerInvariant() //#3

(2) and (3) are both incorrect when it comes to exotic languages and strange characters. The Turkish "I" is the classical example.

www.un.org/spanish/ecosoc 航道使用第1号,甚至在哈希姆。

(非常特殊的情况除外)

Answer 4

应当指出,<代码>Regex.Match(s1, s2, RegexOptions. IgnoreCase)不是在一般情况下检查对案件敏感的平等的一种安全方法。审议s2 is *>的.Regex.Match将始终如一地交回s!

Answer 5

This may be the most extreme case of premature optimization I ve ever seen. Trust me, you will never run into a situation where this issue will be relevant.

而不要听从所有那些告诉你们的人,不要因为“the慢”而避开reg。 Badly written regexes can actual hog resources about awful, but that s thefall of whoever written the regex. 合理精心设计的规章,对于绝大多数任务的人来说,是足够快的。

Answer 6

这里对拟议的3种方法进行了小的比较:

Regex: 282ms ToLower: 67ms Equals: 34ms

public static void RunSnippet()
{
    string s1 = "Abc";
    string s2 = "ABC";

    // Preload
    compareUsingRegex(s1, s2);
    compareUsingToLower(s1, s2);
    compareUsingEquals(s1, s2);

    // Regex
    Stopwatch swRegex = Stopwatch.StartNew();
    for (int i = 0; i < 300000; i++) 
        compareUsingRegex(s1, s2);
    Console.WriteLine(string.Format("Regex: {0} ms", swRegex.ElapsedMilliseconds));

    // ToLower
    Stopwatch swToLower = Stopwatch.StartNew();
    for (int i = 0; i < 300000; i++) 
        compareUsingToLower(s1, s2);
    Console.WriteLine(string.Format("ToLower: {0} ms", swToLower.ElapsedMilliseconds));

    // ToLower
    Stopwatch swEquals = Stopwatch.StartNew();
    for (int i = 0; i < 300000; i++) 
        compareUsingEquals(s1, s2);
    Console.WriteLine(string.Format("Equals: {0} ms", swEquals.ElapsedMilliseconds));
}

private static bool compareUsingRegex(string s1, string s2) 
{
    return Regex.IsMatch(s1, s2, RegexOptions.IgnoreCase);
}

private static bool compareUsingToLower(string s1, string s2) 
{
    return s1.ToLower() == s2.ToLower();
}

private static bool compareUsingEquals(string s1, string s2) 
{
    return s1.Equals(s2, StringComparison.CurrentCultureIgnoreCase);
}

Answer 7

比较速度较快,但不能转换为低级或高级案件,然后比较,最好采用平等比较办法,使情况敏感。例如:

        s1.Equals(s2, StringComparison.OrdinalIgnoreCase)

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