Merge Duplicate list entries into one and display quantity in C# -

i have list below.

list<product> productlist = new list<product>(); 

and product class looks follows.

public class product {     public int id { get; set; }     public string productname { get; set; }     public int quantity { get; set; } } 

now if user inserts duplicate list entries identified id, how able merge follows

product name       qty coke                2 pepsi               7 

you use linq build new set of products:

var results = productlist                  .groupby(p => p.id)                  .select(g => new product { id = g.key, productname = g.first().productname, quantity = g.sum(i => i.quantity) })                  .tolist(); 

if need product names , quantities, can use:

var results = productlist                  .groupby(p => p.productname)                  .select(g => new { productname = g.key, quantity = g.sum() });  foreach(var product in results) {      console.writeline("{0}      {1}", product.productname, product.quantity); }