C# 中的 Struct v/s Class - 请解释行为 [英] Struct v/s Class in C# - Please explain the behavior

问题描述

谁能解释一下这种行为

  class testCompile
    {
       /*
        *   Sample Code For Purpose of Illustration
        */
       struct person 
       {
           public int age;
           public string name;

       }

        static void Main(string[] args)
        {
            List<person> Listperson = new List<person>();
            person myperson = new person();

            for (int i = 1; i <= 2; i++)
            { 
                //Assignment
                myperson.age = 22+i;
                myperson.name = "Person - " + i.ToString();
                Listperson.Add(myperson);
            }
            int x = 0;
            while (x < Listperson.Count)
            {
                //Output values
                Console.WriteLine("{0} - {1}", Listperson[x].name, Listperson[x].age);
                x++;
            }
        }
    }

/*  
    Output:
    Person - 1 - 23
    Person - 2 - 24
*/

为什么我的类的输出与结构的输出不同?

Why am I not getting the same output for a class as that of a struct?

class testCompile
    {
       /*
        *   Sample Code For Purpose of Illustration
        */
       class person 
       {
           public int age;
           public string name;

       }

        static void Main(string[] args)
        {
            List<person> Listperson = new List<person>();
            person myperson = new person();

            for (int i = 1; i <= 2; i++)
            { 
                //Assignment
                myperson.age = 22+i;
                myperson.name = "Person - " + i.ToString();
                Listperson.Add(myperson);
            }
            int x = 0;
            while (x < Listperson.Count)
            {
                //Output values
                Console.WriteLine("{0} - {1}", Listperson[x].name, Listperson[x].age);
                x++;
            }
        }
    }
/*  
    Output:
    Person - 2 - 24
    Person - 2 - 24 
*/

推荐答案

类是引用类型，结构是值类型.

Classes are reference types, structs are value types.

当值类型作为参数传递给方法时，它的副本将被传递.这意味着您要添加 Person 结构的两个完全独立的副本，循环中的每一次通过一个副本.

When a value type is passed to a method as a parameter, a copy of it will be passed through. That means that you add two completely separate copies of the Person struct, one for each pass in the loop.

当引用类型作为参数传递给方法时，引用将被传递.这意味着您将引用的两个副本添加到同一个内存位置(到同一个 Person 对象) - 当对这个对象进行更改时，您会看到它反映在两个引用，因为它们都引用同一个对象.

When a reference type is passed to a method as a parameter, the reference will be passed through. That mean that you add two copies of the reference to the same memory location (to the same Person object) - when making changes to this one object, you see it reflected in both references since they both reference the same object.

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