String.Contains() 是否比 String.IndexOf() 快?

Is String.Contains() faster than String.IndexOf()?(String.Contains() 是否比 String.IndexOf() 快?)

问题描述

I have a string buffer of about 2000 characters and need to check the buffer if it contains a specific string.
Will do the check in a ASP.NET 2.0 webapp for every webrequest.

Does anyone know if the String.Contains method performs better than String.IndexOf method?

    // 2000 characters in s1, search token in s2
    string s1 = "Many characters. The quick brown fox jumps over the lazy dog"; 
    string s2 = "fox";
    bool b;
    b = s1.Contains(s2);
    int i;
    i = s1.IndexOf(s2);

Fun fact

Contains calls IndexOf:

public bool Contains(string value)
{
    return (this.IndexOf(value, StringComparison.Ordinal) >= 0);
}

Which calls CompareInfo.IndexOf, which ultimately uses a CLR implementation.

If you want to see how strings are compared in the CLR this will show you (look for CaseInsensitiveCompHelper).

IndexOf(string) has no options and Contains()uses an Ordinal compare (a byte-by-byte comparison rather than trying to perform a smart compare, for example, e with é).

So IndexOf will be marginally faster (in theory) as IndexOf goes straight to a string search using FindNLSString from kernel32.dll (the power of reflector!).

Updated for .NET 4.0 - IndexOf no longer uses Ordinal Comparison and so Contains can be faster. See comment below.

这篇关于String.Contains() 是否比 String.IndexOf() 快?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！