List Collection Class

Question

Hello let me describe i don't have any errors in my code , i am just asking a very basic question here RELATED TO list collection class let see i have a class called customer

class customer
    {
        public int Id { get; set; }
        public string  Name { get; set; }
        public int Salary { get; set; }
    }

in my main method i created an array of customer and initialize those properties that is present in my customer class

 static void Main(string[] args)
        {
            customer[] customers = new customer[3];
            customers[0] = new customer
            {
                Id = 1,
                Name = "A",
                Salary = 30000
            };
            customers[1]=new customer
            {
                Id = 2,
                Name = " B",
                Salary = 50000
            };
            customers[2] = new customer
            {
                Id = 3,
                Name = "C",
                Salary = 90000
            };
            List<customer> Cust= new List<customer>(2);
            Cust.Add(customers[0]);
            Cust.Add(customers[1]);
            Cust.Add(customers[2]);
            for (int i = 0; i < Cust.Count; i++)
            {
                customer C = Cust[i];
                Console.WriteLine("Id = {0} & Name = {1} & Salary = {2}",C.Id,C.Name,C.Salary);
            }
                Console.ReadLine();

        }

Okay! so this code is working so perfectly nice , but my question is that at last we created a list called cust and add all the custemers in to it , so why is it necessary to make another object with type customer as i did in for loop

customer C = Cust[i];

why can i don't call my code like this

console.WriteLine{Cust[i]}

As far as i know when we create object of the class than we can easily acces the code inside that class with that instance variable . so why not here?

Answer 1

To do what you were asking to do, you would first need to override the ToString() method on your class. The ToString() method will be called implicitly by Console.WriteLine:

class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Salary { get; set; }

    public override string ToString()
    {
        return string.Format("Id = {0} & Name = {1} & Salary = {2}", Id, Name, Salary);
    }
}

Now that you have a default way to represent a customer as a string, you can do exactly what you were asking to do:

for (int i = 0; i < Cust.Count; i++)
{
    Console.WriteLine(Cust[i]);
}

And, now that you have this, you can do it in an even easier way. The following will implicitly pass each item to Console.WriteLine(), which will call the item's ToString() method:

customers.ForEach(Console.WriteLine);

If for some reason you DON'T want to override the ToString method, you can still access the instance properties using the index without creating a new object, like so:

for (int i = 0; i < Cust.Count; i++)
{
    Console.WriteLine("Id = {0} & Name = {1} & Salary = {2}",
        Cust[i].Id, Cust[i].Name, Cust[i].Salary);
}

Answer 2

In your for loop, you're not creating a new customer, you're just creating a reference to the existing one:

for (int i = 0; i < Cust.Count; i++)
{
    customer C = Cust[i]; //<- not new, just a reference to the customer at index
    Console.WriteLine("Id = {0} & Name = {1} & Salary = {2}",C.Id,C.Name,C.Salary);
}

A more concise way to loop is to use foreach instead of for (NOTE: using C# 6.0 string interpolation):

foreach(var c in Cust)
    Console.WriteLine($"Id = {c.Id} & Name = {c.Name} & Salary = {c.Salary}");