Detailed explanation of classes and objects in C #

In C #, class (Class) is one of the basic building blocks of object-oriented programming.

A class is a data structure that encapsulates data (fields) and methods (functions) that manipulate that data.

Objects can be created through classes, and objects are instances of classes.

This article will explain in detail how to define classes and objects in C #, and manipulate object data through properties, methods, and constructors, and show how to design object-oriented programming in conjunction with encapsulation.

Define classes and objects.

First, let's look at a simple example of defining a class that represents "student":

using System;

namespace ExampleNamespace
{
    // 定义一个Student类
    public class Student
    {
        // 私有字段
        private string name;
        private int age;
        private string studentId;

        // 公共属性
        public string Name
        {
            get { return name; }
            set { name = value; }
        }

        public int Age
        {
            get { return age; }
            set { age = value; }
        }

        public string StudentId
        {
            get { return studentId; }
            set { studentId = value; }
        }

        // 构造函数
        public Student(string name, int age, string studentId)
        {
            this.name = name;
            this.age = age;
            this.studentId = studentId;
        }

        // 方法
        public void DisplayInfo()
        {
            Console.WriteLine($"Name: {name}, Age: {age}, Student ID: {studentId}");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            // 创建Student对象并初始化
            Student student = new Student("John Doe", 20, "S123456");

            // 使用属性和方法操作对象数据
            student.DisplayInfo(); // 输出: Name: John Doe, Age: 20, Student ID: S123456

            // 修改属性值
            student.Name = "Jane Smith";
            student.Age = 21;
            student.StudentId = "S654321";

            // 再次调用方法显示更新后的信息
            student.DisplayInfo(); // 输出: Name: Jane Smith, Age: 21, Student ID: S654321
        }
    }
}

Code parsing.

1. # Definition class #: public class StudentDefines a StudentClass.

2. # private field #: private string name;The private field of the class is defined, which is used to store the student's name, age and student number.

These fields can only be accessed within the class.

3. # public property #: public string NameEtc. Defines public properties that provide access to and modification of private fields.

Pass getSumsetKeywords, we can control read and write permissions to these fields.

4. # Constructor #: public Student(string name, int age, string studentId)Is a constructor that initializes fields when an object is created.

The constructor has the same name as the class name and has no return type.

5. # method #: public void DisplayInfo()Is a public method for printing student details.

6. # Create Object #: in MainMethod, through new Student("John Doe", 20, "S123456")Created a StudentObject, and use the constructor to initialize its fields.

7. # Operation Object Data #: Operate on object data through properties and methods, such as modifying property values and calling methods to display information.

Encapsulation.

Encapsulation is one of the core concepts of object-oriented programming, which refers to binding the state (fields) and behavior (methods) of an object together and hiding the internal implementation details of the object.

In the above example, StudentThe fields of the class are declared private ( private), only through public properties ( public) to access and modify.

This design protects the internal state of the object and prevents external code from directly modifying fields, thereby improving the security and maintainability of the code.

Practical application.

In actual development, the application of classes and objects is very extensive.

The following are some common application scenarios: 1. # User Interface #: When developing graphical user interface (GUI) applications, classes can be used to represent controls such as windows, buttons, text boxes, etc.

Each control has its own properties (such as size, color, text content) and methods (such as click event processing).

2. # Database Operation #: In database applications, classes can be used to represent database tables or records.

Each class corresponds to a table or a record containing related fields and methods.

3. # Business Logic #: In enterprise-level applications, classes can be used to represent business entities (such as orders, customers, products) and business rules (such as discount calculation, inventory management).

4. # Game Development #: In game development, classes can be used to represent characters, enemies, props and other elements in the game.

Each element has its own attributes (such as health, attack power) and methods (such as movement, attack).

Summarize.

Through the introduction of this article, we learned how to define classes and objects in C #, and manipulate the data of objects through properties, methods and constructors.

At the same time, we also showed how to design object-oriented programming in combination with encapsulation to improve code security and maintainability.

I hope this article will help you understand and apply the classes and objects in C #!