Linq Coding Practice

 

Linq Question

Concept with exapmle

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
	public static void Main()
	{
		// Linq question
		List<int> num = new List<int>() {1,2,4,5,6,7,2,6};
		
		//Q1- distinct numbers form the list using LINQ
		IEnumerable<int> unqNum = num.Distinct().ToList();
		
		foreach(var n in unqNum){
			Console.Write(n + " ");
		}
		Console.WriteLine();
		// filtering 
		// Q2- find Even & odd numbers from list
		IEnumerable<int> evenNum = num.Where(n => n%2==0).ToList();
		IEnumerable<int> oddNum = num.Where(n => n%2!=0).ToList();
		
		Console.Write("Even numbers: ");
		foreach(var n in evenNum){
			Console.Write(n + " ,");
		}
		Console.WriteLine();
		Console.Write("odd numbers: ");
		foreach(var n in oddNum){
			Console.Write(n + ", ");
		}
		Console.WriteLine();
		// sorting
		// Assending order
		IEnumerable<int> ascNum = num.OrderBy(x=> x).ToList();
		Console.Write("Assinding order: ");
		foreach(var n in ascNum){
			Console.Write(n + " ");
		}
		Console.WriteLine();
		// dessinding order
		IEnumerable<int> descNum = num.OrderByDescending(x=>x).ToList();
		Console.Write("dessinding order: ");
		foreach(var n in descNum){
			Console.Write(n + " ");
		}
		Console.WriteLine();
		
		// first() and firstOrDefault()
		
		var first = num.First();
		Console.WriteLine("first: "+ first);
		var EmptyList = new List<int>() {};
		//var firstEmpty = EmptyList.First(); // InvalidOperationException - Sequence contain no elements 
		//Console.WriteLine("first: "+ firstEmpty);
		var firstEmpty_ = EmptyList.FirstOrDefault(); // similar LastOrDefault();
		Console.WriteLine("first: "+ firstEmpty_);
		
		// Any() - any number satisfy the condition return true or false
		// All() - all number satisfy the condition return true or false
		var secList = new List<int>() {3,5,7};
		var checkEven = num.Any(x=> x%2==0); // return true
 		var checkEvenInSecList = secList.Any(x=> x%2==0); // return false
		Console.WriteLine("is Even num in numList: {0}, is Even num in secList: {1}",checkEven,checkEvenInSecList);
	
		// Skip() & Take()
		
		//first 3 Element
		var fistThree = num.Take(3).ToList();
		
		foreach(var n in fistThree){
			Console.Write(n + " ");
		}
		Console.WriteLine();
		// skip first 2 element from list
		var skipFirst2 = num.Skip(2).ToList();
		foreach(var n in skipFirst2){
			Console.Write(n + " ");
		}
		Console.WriteLine();
		// Zip - merge element at crospondind position
		var numbers = new List<int>() {1,2,3};
		var latters = new List<char>() {'a','b','c'};
		var res = numbers.Zip(latters, (num, latter) => $"{num}-{latter}");
		foreach(var n in res){
			Console.Write(n + " "); // give result 1-a 2-b 3-c 
		}
		Console.WriteLine();
		
		//aggragate function
		var intList = new List<int>() {1,2,3,4,5};
		//M-1: Built-in aggragate fun 
		//Sum: int total = num.Sum();
		//Average: double avg = num.Average();
		//Min / Max: int smallest = num.Min(); / int largest = num.Max();
		//Count: int totalItems = num.Count();
		int total = intList.Sum();
		Console.WriteLine("Total :"+ total);
		//M-2: The Custom .Aggregate() Method
		//This method works by keeping track of an accumulator value as it moves through the list.
		int totalInt = intList.Aggregate((acc, next) => acc + next);
		Console.WriteLine("Total :"+ totalInt);
		//Practical Example: Building a String
		//You can also use it to format your output—like turning your list into a comma-separated string: 
		string intListFormate = intList
			.Select(x=> x.ToString())
			.Aggregate((acc,next) => acc + ", "+ next);
		Console.WriteLine("String Formate :"+ intListFormate);
	}
}

OutPUT:

1 2 4 5 6 7 
Even numbers: 2 ,4 ,6 ,2 ,6 ,
odd numbers: 1, 5, 7, 
Assinding order: 1 2 2 4 5 6 6 7 
dessinding order: 7 6 6 5 4 2 2 1 
first: 1
first: 0
is Even num in numList: True, is Even num in secList: False
1 2 4 
4 5 6 7 2 6 
1-a 2-b 3-c 
Total :15
Total :15
String Formate :1, 2, 3, 4, 5

SelectMany

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
	public static void Main()
	{
		// Select many 
		var order = new List<Order>()
		{
			new Order {Id=1, Product= new List<string> {"P1","P2"}},
			new Order { Id= 2, Product= new List<string> {"P2","P3"}}
		};
		Console.Write(" ");
		var allproduct = order.SelectMany(order=> order.Product).Distinct().ToList();
		foreach(var item in allproduct){
			Console.Write( item +" "); // output: P1 P2 P3
		}
		
	}
	
}
public class Order{
	public int Id {get; set;}
	public List<string> Product {get; set;}
}

JOIN

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
	public static void Main()
	{
		 
		var customers = new List<Customer>
		{
			new Customer {Id =1, Name = "SKS"},
			new Customer {Id =2, Name = "ACS"}
		};
		var orders = new List<Order>
		{
			new Order { CustId=1, Amount= 300.00},
			new Order { CustId=2, Amount= 400.00}
		};
		// Join
		var customerOrder = customers.Join(
			orders,
			customer => customer.Id, // Key from Customers
			order => order.CustId, // Key from Orders
			(customer, order) => new
			{
				CustomerName = customer.Name,
				OrderAmount = order.Amount
			});
		
		foreach(var co in customerOrder)
		{
			Console.WriteLine($"{co.CustomerName}- {co.OrderAmount}");
		}
	}
}
public class Customer{
	public int Id {get; set;}
	public string Name {get; set;}
}
public class Order{
	public int CustId {get;set;}
	public double Amount {get;set;}
}

// OUTPUT : SKS- 300 ACS- 400