ตัวสร้างและสมาชิก static

ภาพรวมตัวสร้างและสแตติก

ตัวสร้างพื้นฐาน

using System;

// Constructor sets required data on creation
public class User
{
  public string Name { get; private set; }
  public int Age { get; private set; }

  public User(string name, int age)
  {
    Name = name;
    Age = age;
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    User u = new User("Ada", 28);
    Console.WriteLine(u.Name + " (" + u.Age + ")");
  }
}

โอเวอร์โหลดและการเชื่อมโยง

using System;

// Overloads let you offer defaults; chain with this(...)
public class Point2D
{
  public int X { get; private set; }
  public int Y { get; private set; }

  public Point2D(int x, int y)
  {
    X = x; Y = y;
  }

  public Point2D(int xy) : this(xy, xy) { } // calls the main constructor
}

public class Program
{
  public static void Main(string[] args)
  {
    Point2D p1 = new Point2D(3, 4);
    Point2D p2 = new Point2D(5); // becomes (5,5)
    Console.WriteLine("p1: " + p1.X + "," + p1.Y);
    Console.WriteLine("p2: " + p2.X + "," + p2.Y);
  }
}

สมาชิกแบบสแตติก

using System;

// Static members live on the type (one copy shared)
public class Counter
{
  private static int _created = 0;   // shared count
  public int Id { get; private set; }

  public Counter()
  {
    _created = _created + 1;
    Id = _created;
  }

  public static int CreatedCount()
  {
    return _created;
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    Counter a = new Counter();
    Counter b = new Counter();
    Console.WriteLine("a.Id=" + a.Id + ", b.Id=" + b.Id);
    Console.WriteLine("Total created = " + Counter.CreatedCount());
  }
}

ตัวสร้างแบบสแตติกและค่าคงที่

using System;

public class AppConfig
{
  public const string AppName = "Demo";      // compile-time constant
  public static readonly DateTime StartedAt; // runtime-initialized once

  // Static constructor: runs once before first use of the type
  static AppConfig()
  {
    StartedAt = DateTime.UtcNow;
  }

  public static string Info()
  {
    return AppName + " started at " + StartedAt.ToString("u");
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    Console.WriteLine(AppConfig.Info());
    Console.WriteLine(AppConfig.Info()); // static ctor ran only once
  }
}

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แนวคิดสมาชิกแบบสแตติก

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