C# Learning Diary 11---Data Type of Enumeration (enum) Type

What I introduced earlier are all value types. After writing so much, I will summarize what a value type is. Simply put, variables of this type directly store the contained value. Here we compare it with the string in C language, char ch[6] = "HC666"; The teacher said that ch is actually used to refer to the address of "HC666", and the data is accessed through the access address. The same is true for string, so the string String in C# is a reference type, not a value type. . This is not the case with the struct type. The variable storage content is changed through direct assignment, so it is a value type.

Value type of enumeration (enum) type:

Enumeration (enum): actually provides an easy-to-remember symbol for a set of logically inseparable integer values. For example, it's Sunday, and I bought a movie ticket to watch a movie. The seat number looked good --- No. 66. I found the seat according to the number, and it was a good seat --- No. 2nd row and 5th row, so I finished watching the movie happily. In fact, the number 66 in the screening room where I am is reflected in row 2 and column 5. This is called an enumeration.

Declare enumeration (enum) type variables:

enum   变量名
                   {
                   标识符列表     
            } ;

Note:

In the identifier list, elements are separated by , comma separated;

Each symbol in the enumeration list represents an integer value, an integer value larger than the previous symbol. By default, the first enumeration symbol represents 0, but of course it can also be modified. ：

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
  
namespace Test  
{  
    class Program  
    {  
        //定义 enum 类型 以0开始递增  
        enum weekday  
            {  
                Sun, Mon, tue, Wed, thu, Fri, Sat    //若要改变默认值只需  （Sun = 2， Mon, tue, Wed, thu, Fri, Sat）以2开始递增+1  
            };  
  
        static void Main(string[] args)  
        {  
            weekday wek;  
            Console.WriteLine("输入0~6一个数字: ");  
            int i = int.Parse(Console.ReadLine());  
  
            wek = (weekday)i;     //强制类型转换，将int类型转化为 weekday 类型  
  
            Console.WriteLine("{0} 是 {1}", i, wek);  
  
        }  
    }  
}

I enter a 0:

I will write specifically about the forced type conversions that appear in the code later in Implicit conversions and explicit conversions I won’t introduce it now.

Comparison of structure (struct) type and enumeration (enum) type:

I have a classmate who always can’t tell the difference between Struct type and enum type. , sometimes I write an error code like this:

enum  wek
{
     int   a,b,c;
   string  d,e,f;
}

In order to avoid the above errors, let me talk about the differences between them: When talking about the struct type, I have already mentioned that the data types in it can be of multiple different types. In other words, the Struct type is a new type composed of different types of data. The value of the structure type variable is composed of each member. values ​​are combined. For example:

  Struct   wek
{
      public  int   a  = 1;
     public  int   b = 2;
}

Determine a variable wek w; At this time, w can be used to indicate that the value of a is 1 (w.a), or it can also indicate that the value of b is 2 (w.b)

The enumeration type is different. A variable of the enumeration type can only take the value of a certain element in the enumeration list at a certain time. For example: in the enum weekday program I wrote earlier, wek can only represent at a certain time A value that cannot represent both Sun and Mon at the same time,

wek = (weekday) 2; At this time, wek can only represent Tue, and cannot represent anything else.

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