Collections are a more powerful form of arrays. In this lesson, we demonstrate an "old style" collection (pointing out its limitations), along with several of the newer, strongly typed generic collections (List<T> and Dictionary<T1, T2>) utilizing the generics syntax.
Before
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace WorkingWithCollections
{
class Program
{
static void Main(string[] args)
{
Car car1 = new Car();
car1.Make = "Oldsmobile";
car1.Model = "Cutlas Supreme";
Car car2 = new Car();
car2.Make = "Geo";
car2.Model = "Prism";
Book b1 = new Book();
b1.Author = "Robert Tabor";
b1.Author = "Microsoft .NET XML Web Services";
b1.ISBN = "0-000-00000-0";
Console.ReadLine();
}
}
class Car
{
public string Make { get; set; }
public string Model { get; set; }
}
class Book
{
public string Title { get; set; }
public string Author { get; set; }
public string ISBN { get; set; }
}
}
After
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace WorkingWithCollections
{
class Program
{
static void Main(string[] args)
{
/*
Car car1 = new Car();
car1.Make = "Oldsmobile";
car1.Model = "Cutlas Supreme";
Car car2 = new Car();
car2.Make = "Geo";
car2.Model = "Prism";
Book b1 = new Book();
b1.Author = "Robert Tabor";
b1.Author = "Microsoft .NET XML Web Services";
b1.ISBN = "0-000-00000-0";
*/
// ArrayLists are dynamically sized, and support other
// cool features like sorting, removing items, etc.
/*
System.Collections.ArrayList myArrayList = new System.Collections.ArrayList();
myArrayList.Add(car1);
myArrayList.Add(car2);
myArrayList.Add(b1);
myArrayList.Remove(b1);
foreach (object o in myArrayList)
{
Console.WriteLine(((Car)o).Make);
}
*/
// Dictionaries allow you to save a key along with
// the value, and also support cool features.
// There are different dictionaries to choose from ...
/*
System.Collections.Specialized.ListDictionary myDictionary
= new System.Collections.Specialized.ListDictionary();
myDictionary.Add(car1.Make, car1);
myDictionary.Add(car2.Make, car2);
myDictionary.Add(b1.Author, b1);
// Easy access to an element using its key
Console.WriteLine(((Car)myDictionary["Geo"]).Model);
// But since its not strongly typed, we can easily break it
// by adding a different type to the dictionary ...
// Obviously, I'm trying to retrieve a book here, and then get its ... model?
Console.WriteLine(((Car)myDictionary["Robert Tabor"]).Model);
*/
/*
List<Car> myList = new List<Car>();
myList.Add(car1);
myList.Add(car2);
//myList.Add(b1);
foreach (Car car in myList)
{
// No casting!
Console.WriteLine(car.Model);
}
*/
/*
Dictionary<string, Car> myDictionary = new Dictionary<string, Car>();
myDictionary.Add(car1.Make, car1);
myDictionary.Add(car2.Make, car2);
Console.WriteLine(myDictionary["Geo"].Model);
*/
//string[] names = { "Bob", "Steve", "Brian", "Chuck" };
Car car1 = new Car() { Make = "Oldsmobile", Model = "Cutlas Supreme" };
Car car2 = new Car() { Make = "Geo", Model = "Prism" };
Car car3 = new Car() { Make = "Nissan", Model = "Altima" };
List<Car> myList = new List<Car>() {
new Car { Make = "Oldsmobile", Model = "Cutlas Supreme"},
new Car { Make = "Geo", Model="Prism"},
new Car { Make = "Nissan", Model = "Altima"}
};
Console.ReadLine();
}
}
class Car
{
public string Make { get; set; }
public string Model { get; set; }
}
class Book
{
public string Title { get; set; }
public string Author { get; set; }
public string ISBN { get; set; }
}
}
Source :
MS Virtual Academy
