Explanation of C value type and reference type

To understand value types and reference types , We first need to know the difference between heap and stack ：

① Stack is the memory space allocated during compilation , So you have to have a clear definition of the stack size in your code ; Heap is the memory space allocated dynamically during the program running , You can determine the size of heap memory to allocate according to the operation of the program

② When it is stored in the stack, it should take care of the storage order , Keep the principle of "first in, last out" , It is a contiguous memory field , Automatically assigned and maintained by the system .
And the heap is disordered , It is a discontinuous memory field, which is controlled and released by the user , If the user does not release , When memory reaches a certain value , Through the garbage collector (GC) To recycle .

• C# The value types of are ： Structure , enumeration , Null type ,byte,short,int,long,float,double,decimal,char,bool ; Value types are stored on the data stack ;

• C# The reference types of include ： Array , User defined classes 、 Interface 、 entrust ,object, character string , Reference types are stored on the heap .

• After understanding the above differences , Let's show the difference in use through examples ：

• Examples of reference types ： Here are two definitions byte Array , Exchange data with consistent subscripts ：

  The code is as follows ：

• static void Main(string[] args)
          {
              byte[] a = new byte[] { 1, 2, 3, 4, 5 };
              byte[] b = new byte[] { 6, 7, 8, 9, 10 };
              ChangeData(a, b);
  
  
              Console.Write($"a The value of the array ：");
              for (int i=0;i<  a.Count();i++)
              {
                  Console.Write($"{a[i]} ");
              }
              Console.WriteLine("\n ***********");
              Console.Write($"b The value of the array ：");
              for (int i = 0; i < b.Count(); i++)
              {
                  Console.Write($"{b[i]} ");
              }
              Console.ReadKey();
          }
  
  
          private static void ChangeData(byte[] aaa, byte[] bbb)
          {
              int tempa = aaa.Count();
              int tempb = bbb.Count();
  
  
              int count = tempa > tempb ? tempb : tempa;
              byte temp = 0;
              for (int i = 0; i < count; i++)
              {
                  temp = aaa[i];
                  aaa[i] = bbb[i];
                  bbb[i] = temp;
              }
          }

• Running results ：

• 

Although we put byte Array passed to method ChangeData To deal with , But after processing a,b Data exchange is realized , Because arrays are reference types , So in the example above aaa and a All point to the same segment of address , So a aaa After change ,a The value of the array has changed .

Examples of value types ：

static void Main(string[] args)
        {
            //byte[] a = new byte[] { 1, 2, 3, 4, 5 };
            //byte[] b = new byte[] { 6, 7, 8, 9, 10 };
            //ChangeData(a, b);


            //Console.Write($"a The value of the array ：");
            //for (int i=0;i<  a.Count();i++)
            //{
            //    Console.Write($"{a[i]} ");
            //}
            //Console.WriteLine("\n ***********");
            //Console.Write($"b The value of the array ：");
            //for (int i = 0; i < b.Count(); i++)
            //{
            //    Console.Write($"{b[i]} ");
            //}


            int a = 5;
            int b = 8;
            ChangeValue(a,b);
            Console.WriteLine($"a Value ：{a}");
            Console.WriteLine($"b Value ：{b}");
            Console.ReadKey();
        }


        //private static void ChangeData(byte[] aaa, byte[] bbb)
        //{
        //    int tempa = aaa.Count();
        //    int tempb = bbb.Count();


        //    int count = tempa > tempb ? tempb : tempa;
        //    byte temp = 0;
        //    for (int i = 0; i < count; i++)
        //    {
        //        temp = aaa[i];
        //        aaa[i] = bbb[i];
        //        bbb[i] = temp;
        //    }
        //}


        private static void ChangeValue(int aaa, int bbb)
        {
            int temp = aaa;
            aaa = bbb;
            bbb = temp;
        }

Running results ：

Let's see after the value exchange aaa and bbb The value has changed. , The original a and b The value of has not changed .