c# - 两个不同的 "strings"是同一个对象实例吗？

Question

代码很容易解释。当我制作 a1 和 b1 时，我预计我会创建两个包含相同文本的不同字符串实例。所以我认为 a1 == b1 会是 true 但 object.ReferenceEquals(a1,b1) 会是 false，但事实并非如此。为什么？

//make two seemingly different string instances
string a1 = "test";
string b1 = "test";         
Console.WriteLine(object.ReferenceEquals(a1, b1)); // prints True. why?

//explicitly "recreating" b2
string a2 = "test";
string b2 = "tes";
b2 += "t";    
Console.WriteLine(object.ReferenceEquals(a2, b2)); // prints False

//explicitly using new string constructor
string a3 = new string("test".ToCharArray());
string b3 = new string("test".ToCharArray());    
Console.WriteLine(object.ReferenceEquals(a3, b3)); // prints False

Answer 1

编译器将文字字符串对象合并为单个实例。这实际上是 required by the specification :

Each string literal does not necessarily result in a new string instance. When two or more string literals that are equivalent according to the string equality operator (Section 7.9.7) appear in the same assembly, these string literals refer to the same string instance.