internal class Program
{
    static void Main(string[] args)
    {
       Book book = new Book();
        book.Title = "Test";
        book.Price = 10;
        //Console.WriteLine((book.Title, book.Price));
        book.Display();
    }
}
class Book
{
   public string Title;
   public decimal Price;
    
    //method
    public void Display() => Console.WriteLine((Title, Price));

}
//=========================
//overloading
class Person
{
    public string SayHi() => "Hi...";
    public string SayHi(string name) => $"Hi {name} ";
}

Person person = new Person();
Console.WriteLine(person.SayHi());
Console.WriteLine(person.SayHi("Mary"));
//=========================
//property
private decimal price;
public decimal Price
{
    get => price;
    set => price = value > 0 ? value : 0;
}
//===========================
//read-only property
public DateTime Time1=DateTime.Now; //field
public DateTime Time2 { // read-only property
    get=>DateTime.Now;
}
public DateTime Time3=>DateTime.Now; //read-only property
//===========================
//auto property
//propfull
//private string title; //field

//public string Title //property
//{
//    get { return title; }
//    set { title = value; }
//}

//prop
public string Title { get; set; }
//=============================
Console.WriteLine(book.Time1);
Console.WriteLine(book.Time2);
Console.WriteLine(book.Time3);
Console.WriteLine(book.Time4);
Thread.Sleep(3000);
Console.WriteLine("============================");
Console.WriteLine(book.Time1);
Console.WriteLine(book.Time2);
Console.WriteLine(book.Time3);
Console.WriteLine(book.Time4);

public DateTime Time1 = DateTime.Now; //field
public DateTime Time2
{ // read-only property
    get => DateTime.Now;
}
public DateTime Time3 => DateTime.Now; //read-only property

public DateTime Time4 { get; set; } = DateTime.Now;
//========================
//partial class
partial class Customer
{
    public string Name { get; set; }

}
partial class Customer
{
    public string Address { get; set; }
}
Customer customer = new Customer();
customer.Name = "Xxx";
customer.Address = "yyy";
Console.WriteLine((customer.Name, customer.Address));
//=============================
//object initializer
Book book = new Book { 
    Title="C#"
};
book.Display();
//=============================
//struct
struct ContactInfo
{
    public string Name;
    public string Title;
    public string Phone;
    public void Display() =>
        Console.WriteLine($"{Name}:{Title}:{Phone}");
}
ContactInfo customer;
customer.Name = "王小明";
customer.Title = "先生";
customer.Phone = "[phone]";
customer.Display();
////=============================
//class vs struct

ContactInfo customer = new ContactInfo();
//ContactInfo customer;            
customer.Name = "王小明";
customer.Title = "先生";
customer.Phone = "[phone]";

ContactInfo customer2 = customer;
customer2.Name = "Xxx";
customer.Display();
Console.WriteLine("====================");
customer2.Display();