ฟิลด์ คุณสมบัติอัตโนมัติ และตัวเริ่มต้นอ็อบเจกต์

ภาพรวมพื้นฐานของคลาส

ฟิลด์ในคลาส

using System;

// Fields store raw data inside a class
public class Player
{
  public string name; // field (usually prefer properties for public APIs)
  public int level;
}

public class Program
{
  public static void Main(string[] args)
  {
    Player p = new Player();
    p.name = "Ada";
    p.level = 1;
    Console.WriteLine("Player " + p.name + " level " + p.level);
  }
}

พร็อพเพอร์ตีอัตโนมัติ

using System;

// Auto-properties generate a hidden backing field
public class Book
{
  public string Title { get; set; }
  public string Author { get; set; }
  public int Pages { get; set; } = 0; // auto-property initializer (C# 6)
}

public class Program
{
  public static void Main(string[] args)
  {
    Book b = new Book();
    b.Title = "Clean Code";
    b.Author = "Robert C. Martin";
    b.Pages = 464;
    Console.WriteLine(b.Title + " by " + b.Author + " (" + b.Pages + " pages)");
  }
}

ตัวเริ่มต้นออบเจ็กต์

using System;

public class Person
{
  public string Name { get; set; }
  public int Age { get; set; }
}

public class Program
{
  public static void Main(string[] args)
  {
    // Object initializer calls set-accessors after construction
    Person p = new Person { Name = "Alan", Age = 30 };
    Console.WriteLine(p.Name + " (" + p.Age + ")");
  }
}

ฟิลด์เทียบกับพร็อพเพอร์ตี

ฟิลด์และพร็อพเพอร์ตีร่วมกัน

using System;

// Private fields + public properties pattern
public class Product
{
  private int _stock;                   // field (internal storage)
  public string Name { get; set; }      // property (public API)
  public int Stock                      // property with simple guard
  {
    get { return _stock; }
    set
    {
      if (value < 0) value = 0; // simple safety for beginners
      _stock = value;
    }
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    Product p = new Product { Name = "Pen", Stock = 5 };
    p.Stock = -3; // setter clamps to 0
    Console.WriteLine(p.Name + " stock = " + p.Stock);
  }
}

แนวคิดพร็อพเพอร์ตีอัตโนมัติ

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