[c# 20问] 1. 何时使用class与struct

POINTS

struct为可以包含数据和函数的值类型

struct为值类型所以不需要堆(heap)而是在栈(stack)上分配空间

struct将数据直接存在struct中，而class只存引用类型的指针

struct适用于小的数据结构

struct会影响性能

struct可以使用new操作可以调用构造器，但是不会在heap上分配内存

struct的构造器只返回struct的值本身(通常分配在stack上)

使用class时，多个变量可以引用同一个对象

使用sturct每个变量都保存自己的数据拷贝，不会相互影响

struct不支持继承，sturct继承自object类型

DEMO

    class Program
    {
        class PointClass
        {
            public int x;
            public int y;
            public PointClass(int x, int y)
            {
                this.x = x;
                this.y = y;
            }
        }
        struct PointStruct
        {
            public int x;
            public int y;
            public PointStruct(int x, int y)
            {
                this.x = x;
                this.y = y;
            }
        }
        static void Main(string[] args)
        {
            PointStruct pointStruct = new PointStruct(10, 10);
            Console.WriteLine("Initial struct values are {0},{1}", pointStruct.x, pointStruct.y);
            ModifyStructPoint(pointStruct);
            Console.WriteLine("After ModifyStructPoint, struct values are {0},{1}", pointStruct.x, pointStruct.y);

            Console.WriteLine();
            PointClass pointClass = new PointClass(10, 10);
            Console.WriteLine("Initial Class values are {0},{1}", pointClass.x, pointClass.y);
            ModifyClassPoint(pointClass);
            Console.WriteLine("After ModifyClassPoint, class values are {0},{1}", pointClass.x, pointClass.y);
            Console.ReadLine();
        }

        private static void ModifyStructPoint(PointStruct pointStruct)
        {
            pointStruct.x = 20;
            pointStruct.y = 20;
            Console.WriteLine("Modified Valuesare {0},{1}", pointStruct.x, pointStruct.y);

        }

        private static void ModifyClassPoint(PointClass pointClass)
        {
            pointClass.x = 20;
            pointClass.y = 20;
            Console.WriteLine("Modified Valuesare {0},{1}", pointClass.x, pointClass.y);
        }
    }