一个对象应该只包含单一的职责,并且该职责被完整地封装在一个类中.

就一个类而已,应该仅有一个引起它变化的原因

单一职责原则实例:

// 单一职责原则C#001
using System;
using System.Collections.Generic;
using System.Ling;
using System.Text;

namespace 单一职责原则C001
{
    public class Animal
    {
        public void Breathe(string animalName)
        {
            console.WriteLine(animalName + "呼吸空气");
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            Animal myAnimal = new Animal();
            
            myAnimal.Breathe("牛");
            myAnimal.Breathe("羊");
            myAnimal.Breathe("猫");
        }
    }
}
// 单一职责原则C#002
using System;
using System.Collections.Generic;
using System.Ling;
using System.Text;

namespace 单一职责原则C002
{
    // 陆地生物
    public class Terrestrial
    {
        public void Breathe(string animalName)
        {
            console.WriteLine(animalName + "呼吸空气");
        }
    }
    
    // 水生生物
    public class Aquatic
    {
        public void Breathe(string animalName)
        {
            console.WriteLine(animalName + "在水中呼吸");
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            Terrestrial myTerrestrial = new Terrestrial();
            myTerrestrial.Breathe("牛");
            myTerrestrial.Breathe("羊");
            myTerrestrial.Breathe("猫");
            
            Aquatic myAquatic = new Aquatic();
            myAquatic.Breathe("鱼");
        }
    }
}
// 单一职责原则C#003
using System;
using System.Collections.Generic;
using System.Ling;
using System.Text;

namespace 单一职责原则C003
{
    public class Animal
    {
        public void Breathe(string animalName)
        {
            if ("鱼".Equals(animalName))
            {
                Console.WriteLine(animalName + "在水中呼吸");
            }
            else
            {
                Console.WriteLine(animalName + "呼吸空气")
            }
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            Animal myAnimal = new Animal();
            myAnimal.Breathe("牛");
            myAnimal.Breathe("羊");
            myAnimal.Breathe("猫");
            myAnimal.Breathe("鱼");
        }
    }
}
// 单一职责原则C#004
using System;
using System.Collections.Generic;
using System.Ling;
using System.Text;

namespace 单一职责原则C004
{
    public class Animal
    {
        public void Breathe01(string animalName)
        {
            Console.WriteLine(animalName + "呼吸空气")
        }
        
        public void Breathe02(string animalName)
        {
            Console.WriteLine(animalName + "在水中呼吸");
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            Animal myAnimal = new Animal();
            myAnimal.Breathe01("牛");
            myAnimal.Breathe01("羊");
            myAnimal.Breathe01("猫");
            myAnimal.Breathe02("鱼");
        }
    }
}

Q.E.D.