static void Main(string[] args)
{
DisplayTemplate.Header("Lambda Expressions");
List <int> numbers = new List <int> {
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
};
// Print even numbers in the list.
foreach (int number in numbers)
{
if (number % 2 == 0)
{
Console.Write(number + " ");
}
}
Console.WriteLine();
// Above method fits in one line, but it is still combination of foreach and if.
// We can use FindAll method of List in combination with delegate.
foreach (int number in numbers.FindAll(delegate(int number) { return(number % 2 == 0); }))
{
Console.Write(number + " ");
}
Console.WriteLine();
// Note that name of variable in foreach, which is 'number', can be either same or different from the name of variable in delegate.
// delegate is a little confusing and hard to remember. To make it short, let's use Lambda Expression.
foreach (int number in numbers.FindAll(number => number % 2 == 0))
{
Console.Write(number + " ");
}
Console.WriteLine();
DisplayTemplate.Footer();
}
static void Main(string[] args)
{
DisplayTemplate.Header("Multi-Threading Programming");
int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
string[] flowers = { "Jasmine", "Rose", "Sunflower", "Lotus", "Lily" };
Thread numberThread = new Thread(new ParameterizedThreadStart(printNumbers));
Thread flowerThread = new Thread(new ParameterizedThreadStart(printFlowers));
numberThread.Start(numbers);
flowerThread.Start(flowers);
DisplayTemplate.Footer();
}
static void Main(string[] args)
{
// Instead of copying and pasting the header and footer of program all the time
// Using a template which is defined in DisplayTemplate class of Templates namespace
// This reduces redundant writing of code. To use this class, add Templates project as a reference.
DisplayTemplate.Header("Fun With Collections");
// There are many in-built collections.
// Use Generic collections to avoid issues.
// List is a dynamic array. The size can increase.
Console.WriteLine("Integer type List Example");
List <int> intArr = new List <int>();
for (int i = 0; i < 10; i++)
{
intArr.Add(i);
}
intArr.ForEach(num => Console.Write(num + " ")); // List can iterate over elements and use lambda expression.
Console.WriteLine();
intArr.RemoveAt(5);
intArr.ForEach(num => Console.Write(num + " "));
Console.WriteLine("\n");
// You can also make a General list. This list contains int, string and double.
List <object> genArr = new List <object>();
genArr.Add(21);
genArr.Add("Mark");
genArr.Add(0.5);
Console.WriteLine("General List Example");
genArr.ForEach(num => Console.WriteLine(num + " : " + num.GetType()));
Console.WriteLine();
// An example of Stack
Stack <int> stack = new Stack <int>();
stack.Push(1);
stack.Push(2);
stack.Push(3);
Console.WriteLine("Stack Example");
Console.WriteLine(stack.Pop());
Console.WriteLine(stack.Peek());
Console.WriteLine();
// An example of Queue
Queue <int> queue = new Queue <int>();
queue.Enqueue(1);
queue.Enqueue(2);
queue.Enqueue(3);
Console.WriteLine("Queue Example");
Console.WriteLine(queue.Dequeue());
Console.WriteLine(queue.Peek());
Console.WriteLine();
// An example of Dictionary. Dictionary is a key-value pair. Key must be unique.
Console.WriteLine("Dictionary Example");
Dictionary <int, string> courses = new Dictionary <int, string>()
{
[101] = "Math", [102] = "Science"
};
courses.Add(103, "Computers");
courses.Add(104, "History");
// Iterate using keys
foreach (int key in courses.Keys)
{
Console.WriteLine(key + " : " + courses[key]);
}
Console.WriteLine();
DisplayTemplate.Footer();
}
static void Main(string[] args)
{
DisplayTemplate.Header("Language Integrated Queries (LINQ)");
DisplayTemplate.Header("LINQ to Objects");
string[] games = { "Skyrim", "Uncharted 4", "The Last Of Us", "The Witcher III", "Control" };
IEnumerable <string> subset = from game in games where game.Contains(" ") orderby game select game;
foreach (string game in subset)
{
Console.WriteLine(game);
}
Console.WriteLine();
// Another way is to use extensions
subset = games.Where(game => game.Contains("The")).OrderBy(game => game).Select(game => game);
foreach (string game in subset)
{
Console.WriteLine(game);
}
Console.WriteLine();
// Instead of using IEnumerable, we can also use var
var sorted = games.OrderBy(game => game).Select(game => game);
foreach (string game in sorted)
{
Console.WriteLine(game);
}
Console.WriteLine();
// LINQ queries are dynamic. Which means, there is no need to define LINQ queries again and again.
games[1] = "God Of War";
foreach (string game in sorted)
{
Console.WriteLine(game);
}
Console.WriteLine();
// Data from LINQ queries can be stored in a collection.
int[] numbers = { 1, 2, 5, 7, 8, 23, 12, 45, 76, 32, 124, 6, 53, 4, 34 };
int[] evenNumbers = numbers.Where(number => number % 2 == 0).OrderBy(number => - number).Select(number => number).ToArray <int>();
foreach (int number in evenNumbers)
{
Console.Write(number + " ");
}
Console.WriteLine();
// Note that values do not change after storing in a collection.
numbers[1] = 25;
foreach (int number in evenNumbers)
{
Console.Write(number + " ");
}
Console.WriteLine("\n");
// LINQ queries over objects of custom classes
List <Student> students = new List <Student>()
{
new Student(101, "Mark", 10),
new Student(105, "John", 12),
new Student(104, "Jack", 10),
new Student(102, "Simon", 12),
new Student(103, "Phillip", 10),
};
Student[] tenthGradeStudents = students.Where(student => student.Grade == 10).OrderBy(student => student.RollNumber).Select(student => student).ToArray <Student>();
foreach (Student student in tenthGradeStudents)
{
Console.WriteLine(student.Name);
}
Console.WriteLine();
// In above example, I am creating array of Student, even though I am just printing names.
// This is very inefficient as Student array takes a lot more space than a string array.
// A better way is to retrieve only required data.
string[] tenthGradeStudentsNames = students.Where(student => student.Grade == 10).OrderBy(student => student.RollNumber).Select(student => student.Name).ToArray <string>();
foreach (string student in tenthGradeStudentsNames)
{
Console.WriteLine(student);
}
Console.WriteLine();
DisplayTemplate.Footer();
}
