比较类型的VALUE和REFERENCE

问题描述

我知道在C#中有很多方法可以比较VALUE和REFERENCES，但是当您尝试比较VALUE或REFERENCE时，我仍然对哪种类型的性能感到困惑.

I know there are a lot of ways to compare VALUE and REFERENCES in C#, but I'm still a bit confused about what type performs what when you try to compare either VALUE or REFERENCE.

字符串示例:

string str = "hello";
string str2 = "hello";

if (str == str2)
{
   Console.WriteLine("Something");
} // Is this a comparison of value?

if (str.Equals(str2))
{
   Console.WriteLine("Something");
} // Is this a comparison of value?

string.ReferenceEquals(str, str2); // Comparison of reference (True)

Console.WriteLine((object)str1 == (object)str2); // Comparison of reference (True)

推荐答案

Equals和==如果未在子类中覆盖/重载，则默认情况下将通过引用进行比较. ReferenceEquals将始终通过引用进行比较.

Equals and == will compare by reference by default if they're not overriden / overloaded in a subclass. ReferenceEquals will always compare by reference.

字符串是一种令人困惑的数据类型，可用于进行此实验，因为它们重载了==来实现值相等.同样，由于它们是不可变的，因此C#通常会将相同的实例重用于相同的文字字符串.在您的代码中，str和str2将是同一对象.

Strings are a confusing data type to use for experimenting with this, because they overload == to implement value equality; also, since they're immutable, C# will generally reuse the same instance for the same literal string. In your code, str and str2 will be the same object.

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