// This class is mutable. Its data can be modified from
// outside the class.
class Customer
{
  // Auto-Impl Properties for trivial get and set
  public double TotalPurchases { get; set; }
  public string Name { get; set; }
  public int CustomerID { get; set; }

  // Constructor
  public Customer(double purchases, string name, int ID)
  {
    TotalPurchases = purchases;
    Name = name;
    CustomerID = ID;
  }
  // Methods
  public string GetContactInfo() {return "ContactInfo";}
  public string GetTransactionHistory() {return "History";}

  // .. Additional methods, events, etc.
}

class Program
{
  static void Main()
  {
    // Intialize a new object.
    Customer cust1 = new Customer ( 4987.63, "Northwind",90108 );

    //Modify a property
    cust1.TotalPurchases += 499.99;
  }
}

public string FirstName { get; set; } = "Jane";

// This class is immutable. After an object is created, 
  // it cannot be modified from outside the class. It uses a 
  // constructor to initialize its properties. 
  class Contact
  {
    // Read-only properties. 
    public string Name { get; }
    public string Address { get; private set; }

    // Public constructor. 
    public Contact(string contactName, string contactAddress)
    {
      Name = contactName;
      Address = contactAddress;        
    }
  }

  // This class is immutable. After an object is created, 
  // it cannot be modified from outside the class. It uses a 
  // static method and private constructor to initialize its properties.  
  public class Contact2
  {
    // Read-only properties. 
    public string Name { get; private set; }
    public string Address { get; }

    // Private constructor. 
    private Contact2(string contactName, string contactAddress)
    {
      Name = contactName;
      Address = contactAddress;        
    }

    // Public factory method. 
    public static Contact2 CreateContact(string name, string address)
    {
      return new Contact2(name, address);
    }
  }

  public class Program
  { 
    static void Main()
    {
      // Some simple data sources. 
      string[] names = {"Terry Adams","Fadi Fakhouri", "Hanying Feng", 
               "Cesar Garcia", "Debra Garcia"};
      string[] addresses = {"123 Main St.", "345 Cypress Ave.", "678 1st Ave",
                 "12 108th St.", "89 E. 42nd St."};

      // Simple query to demonstrate object creation in select clause. 
      // Create Contact objects by using a constructor. 
      var query1 = from i in Enumerable.Range(0, 5)
            select new Contact(names[i], addresses[i]);

      // List elements cannot be modified by client code. 
      var list = query1.ToList();
      foreach (var contact in list)
      {
        Console.WriteLine("{0}, {1}", contact.Name, contact.Address);
      }

      // Create Contact2 objects by using a static factory method. 
      var query2 = from i in Enumerable.Range(0, 5)
             select Contact2.CreateContact(names[i], addresses[i]);

      // Console output is identical to query1. 
      var list2 = query2.ToList();

      // List elements cannot be modified by client code. 
      // CS0272: 
      // list2[0].Name = "Eugene Zabokritski"; 

      // Keep the console open in debug mode.
      Console.WriteLine("Press any key to exit.");
      Console.ReadKey();        
    }
  }

  Terry Adams, 123 Main St.
  Fadi Fakhouri, 345 Cypress Ave.
  Hanying Feng, 678 1st Ave
  Cesar Garcia, 12 108th St.
  Debra Garcia, 89 E. 42nd St.