asp.net - Display Parent Id once with its multiple child records in a list -

invoice no common multiple products,one invoice number have many products , same products used in other invoices , data unsorted.i know sort data confused how display result on html 1 in picture below.

and on have in list mentioned below :

static void main(string[] args)     {          list<program> listdata = new list<program>();         listdata.add(new program { invoiceno=001, product="product1"});         listdata.add(new program { invoiceno = 001, product = "product2" });         listdata.add(new program { invoiceno = 001, product = "product3" });         listdata.add(new program { invoiceno = 001, product = "product4" });         listdata.add(new program { invoiceno = 001, product = "product5" });         listdata.add(new program { invoiceno = 002, product = "product1" });         listdata.add(new program { invoiceno = 003, product = "product1" });         listdata.add(new program { invoiceno = 004, product = "product1" });         listdata.add(new program { invoiceno = 004, product = "product2" });         listdata.add(new program { invoiceno = 004, product = "product3" });            foreach (var item in listdata)         {             console.writeline(string.format("invoice no : {0} product : {1}",item.invoiceno,item.product));           }         console.readline();     }