两种不同字符串比较方法的性能对比
最近比较关注C#书写出来的代码性能问题,越研究就越觉得很有意思。
在日常的编程过程总,由于编程需要,我们经常会比较两个字符串是否相等,然后再做相应的处理。代码书写起来是觉得很爽,不是吗?if (a==b) then ……else……但是有没有更快的方式呢?为此查阅了一些资料了MSDN文档。当我们调用 a==b的时候,通过IL代码可以看到内部实际上调用了String.Equals(string,string)这个方法
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答案是有的。
.Net 2.0中新增了一个StringComparison枚举类型,实际上我们大多数的字符串比较是和语言别无关的,我们应该使用Ordinal和OrdinalIgnoreCase两个枚举值。处于性能考虑,在字符串比较时不应该直接使用==操作符,而应该使用
bool Equals(string value, StringComparison comparisonType)
bool Equals(string a, string b, StringComparison comparisonType)
为此,我进行了一个测试,看看不等的==操作符和String.Equals方法之间的性能差别有多大。
测试代码:
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然后运行下面的代码:
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算出平均值之后,两者在速度上相差46.675%。
呵呵,差别惊人阿!