Mastering C# List: A Comprehensive Reference

Understanding the C# List<T>

• The List<T> is a collection of strongly typed objects that can be accessed by index and includes methods for sorting, searching, and modifying the list.
• It is the generic version of the ArrayList, found within the System.Collections.Generic namespace.
• The List<T> performs faster and is less error-prone than the ArrayList.
• Because it is a generic collection, you must specify a type parameter for the data it stores.

Creating a List and Adding Elements

List<int> primeNumbers = new List<int>();
primeNumbers.Add(1); // Adding elements using Add() method
primeNumbers.Add(3);
primeNumbers.Add(5);
primeNumbers.Add(7);

Using Collection Initializer Syntax

var bigCities = new List<string>()
{
    "New York",
    "London",
    "Mumbai",
    "Chicago"
};

Adding Custom Class Objects

var students = new List<Student>()
{
    new Student(){ Id = 1, Name="Bill"},
    new Student(){ Id = 2, Name="Steve"},
    new Student(){ Id = 3, Name="Ram"},
    new Student(){ Id = 4, Name="Abdul"}
};

Accessing a List by Index

List<int> numbers = new List<int>() { 1, 2, 5, 7, 8, 10 };
Console.WriteLine(numbers[0]); // prints 1
Console.WriteLine(numbers[1]); // prints 2
Console.WriteLine(numbers[2]); // prints 5
Console.WriteLine(numbers[3]); // prints 7

Accessing a List Using LINQ ForEach

List<int> numbers = new List<int>() { 1, 2, 5, 7, 8, 10 };
// Using foreach LINQ method
numbers.ForEach(num => Console.WriteLine(num + ", "));
// prints 1, 2, 5, 7, 8, 10,

Accessing a List Using a For Loop

List<int> numbers = new List<int>() { 1, 2, 5, 7, 8, 10 };
// Using for loop
for(int i = 0; i < numbers.Count; i++)
    Console.WriteLine(numbers[i]);

Accessing Custom Class Objects by Index

var students = new List<Student>()
{
    new Student(){ Id = 1, Name="Bill"},
    new Student(){ Id = 2, Name="Steve"},
    new Student(){ Id = 3, Name="Ram"},
    new Student(){ Id = 4, Name="Abdul"}
};
Console.WriteLine(students[0].Id);   // prints 1
Console.WriteLine(students[0].Name); // prints Bill

Accessing Custom Objects via LINQ Query

var students = new List<Student>()
{
    new Student(){ Id = 1, Name="Bill"},
    new Student(){ Id = 2, Name="Steve"},
    new Student(){ Id = 3, Name="Ram"},
    new Student(){ Id = 4, Name="Abdul"}
};
// Get all students whose name is Bill
var result = from s in students
             where s.Name == "Bill"
             select s;
foreach(var student in result)
    Console.WriteLine(student.Id + ", " + student.Name);