C#学习2

11. 面向对象编程进阶
    继承
    csharp
    // 基类
    public class Animal
    {
    public string Name

    public virtual void Speak()
    {
    Console.WriteLine("动物发出声音");
    }
    }

// 派生类
public class Dog : Animal
{
public override void Speak()
{
Console.WriteLine("汪汪！");
}
}

// 使用
Dog dog = new Dog { Name = "Buddy" };
dog.Speak(); // 输出：汪汪！
抽象类和接口
csharp
// 抽象类
public abstract class Shape
{
public abstract double CalculateArea();
}

// 接口
public interface IDrawable
{
void Draw();
}

// 实现
public class Circle : Shape, IDrawable
{
public double Radius { get; set; }

public override double CalculateArea()
{
    return Math.PI * Radius * Radius;
}

public void Draw()
{
    Console.WriteLine("绘制圆形");
}

}
12. 属性和访问器
csharp
public class Person
{
private string name;
private int age;

// 自动属性
public string Email { get; set; }

// 完整属性
public string Name
{
    get { return name; }
    set 
    { 
        if (!string.IsNullOrEmpty(value))
            name = value; 
    }
}

// 只读属性
public int BirthYear { get; private set; }

// 计算属性
public bool IsAdult => age >= 18;

}
13. 委托和事件
csharp
// 委托定义
public delegate void MessageHandler(string message);

public class Publisher
{
// 事件定义
public event MessageHandler OnMessageSent;

public void SendMessage(string message)
{
    Console.WriteLine($"发送消息: {message}");
    OnMessageSent?.Invoke(message); // 触发事件
}

}

public class Subscriber
{
public void HandleMessage(string message)
{
Console.WriteLine($"收到消息: {message}");
}
}

// 使用
var publisher = new Publisher();
var subscriber = new Subscriber();

publisher.OnMessageSent += subscriber.HandleMessage;
publisher.SendMessage("Hello World!");
14. LINQ (语言集成查询)
csharp
List numbers = new List { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

// 查询语法
var evenNumbers = from num in numbers
where num % 2 == 0
select num;

// 方法语法
var squares = numbers.Where(n => n % 2 == 0)
.Select(n => n * n);

// 更多LINQ操作
var firstNumber = numbers.First();
var lastNumber = numbers.Last();
var maxNumber = numbers.Max();
var orderedNumbers = numbers.OrderBy(n => n);
var groupedNumbers = numbers.GroupBy(n => n % 2 == 0 ? "偶数" : "奇数");
15. 泛型
csharp
// 泛型类
public class Repository
{
private List items = new List();

public void Add(T item)
{
    items.Add(item);
}

public T Get(int index)
{
    return items[index];
}

}

// 泛型方法
public static T Max(T a, T b) where T : IComparable
{
return a.CompareTo(b) > 0 ? a : b;
}

// 使用
var stringRepo = new Repository();
stringRepo.Add("Hello");

var intRepo = new Repository();
intRepo.Add(42);