c# - Object.ReferenceEquals 为匹配的字符串返回 true

Question

我正在使用 Mono，在比较两个字符串的引用时遇到了一个有趣的结果。下面的代码演示了一个例子:

using System;

class Program
{
    static void Main()
    {
        String s1 = "asd";
        String s2 = "asd";
        Console.WriteLine("Reference Equals: {0}", Object.ReferenceEquals(s1, s2));

        Console.ReadLine();
    }
}

为真。

有趣的是，两个字符串具有相同的值，但显然它们指的是两个不同的实例。这是怎么回事？

mono --version : Mono JIT 编译器版本 3.2.6OS X 10.9.2

Answer 1

http://msdn.microsoft.com/en-us/library/system.string.intern.aspx

The common language runtime conserves string storage by maintaining a table, called the intern pool, that contains a single reference to each unique literal string declared or created programmatically in your program. Consequently, an instance of a literal string with a particular value only exists once in the system.

下面显示了当字符串不是从 string literal 创建时的行为.

    static void Main(string[] args)
    {
        var string1 = new string(new []{'c'});
        var string2 = new string(new []{'c'});
        Console.WriteLine(string1.Equals(string2));                 //true
        Console.WriteLine(Object.ReferenceEquals(string1,string2)); //false
    }