Write a program in C# Sharp to generate a Left Join between two data sets

using System;
using System.Linq;
using System.Collections.Generic;
 
class  LinqExercise26
{
    static void Main(string[] args)
    {
        
        List<Item_mast> itemlist = new List<Item_mast>
	        {  
           new Item_mast { ItemId = 1, ItemDes = "Biscuit  " }, 
           new Item_mast { ItemId = 2, ItemDes = "Chocolate" }, 
           new Item_mast { ItemId = 3, ItemDes = "Butter   " },  
           new Item_mast { ItemId = 4, ItemDes = "Brade    " },  
           new Item_mast { ItemId = 5, ItemDes = "Honey    " }  
            }; 
		  
        List<Purchase> purchlist = new List<Purchase>
	        {  
           new Purchase { InvNo=100, ItemId = 3,  PurQty = 800 }, 
           new Purchase { InvNo=101, ItemId = 2,  PurQty = 650 }, 
           new Purchase { InvNo=102, ItemId = 3,  PurQty = 900 },  
           new Purchase { InvNo=103, ItemId = 4,  PurQty = 700 },
		   new Purchase { InvNo=104, ItemId = 3,  PurQty = 900 },  
           new Purchase { InvNo=105, ItemId = 4,  PurQty = 650 },  		   
           new Purchase { InvNo=106, ItemId = 1,  PurQty = 458 }  
            }; 
	
            Console.Write("\nLINQ : Generate a Left Join between two data sets : "); 
            Console.Write("\n--------------------------------------------------\n");
			Console.Write("Here is the Item_mast List : ");
			Console.Write("\n-------------------------\n");
			
			 foreach (var item in itemlist)
				{
				Console.WriteLine(
				"Item Id: {0}, Description: {1}",
				item.ItemId,
				item.ItemDes);
				}

			Console.Write("\nHere is the Purchase List : ");
			Console.Write("\n--------------------------\n");
			
			 foreach (var item in purchlist)
				{
				Console.WriteLine(
				"Invoice No: {0}, Item Id : {1},  Quantity : {2}",
				item.InvNo,
				item.ItemId,
				item.PurQty);
				}

            Console.Write("\nHere is the list after joining  : \n\n");


           var leftOuterJoin = from itm in itemlist
            		join prch in purchlist
            		on itm.ItemId equals prch.ItemId
            		into a
            			from b in a.DefaultIfEmpty(new Purchase())
            			select new
            			{
                		itid=itm.ItemId,
               			itdes = itm.ItemDes,
                		prqty=b.PurQty
            			};

		    Console.WriteLine("Item ID\t\tItem Name\tPurchase Quantity");
			Console.WriteLine("-------------------------------------------------------");
			foreach (var data in leftOuterJoin)  
			{  
				Console.WriteLine(data.itid + "\t\t" + data.itdes + "\t\t" + data.prqty);  
			}           
             Console.ReadLine();
    }
}
public class Item_mast
{
    public int ItemId { get; set; }
    public string ItemDes { get; set; }
}

public class Purchase
{
    public int InvNo { get; set; }
    public int ItemId { get; set; }
    public int PurQty { get; set; }
}