check if values in datagridview cells exists in another table

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace console_poc
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Entity> lstDBData = new List<Entity>();
            // fetch all the db data from that table which u want to compare and store it in a list
            // or a datatable for LINQ i have used List<T>


            List<Entity> lstUploadData = new List<Entity>();
            // store the excel upload data in this list

            List<Entity> lstDataWhichExistsInDb = new List<Entity>();
            // this list will store the data which is available in the db

            List<Entity> lstDataWhichDoesNotExistsInDb = new List<Entity>();
            // this list will store the data which is not available in the db

            // processs..
            // storing the existing db data in one list and new value in another list
            lstUploadData.ForEach(k =>
                {
                    var item = lstDBData.FirstOrDefault(l => l.Column1 == k.Column1 && l.Column2 == k.Column2);
                    if (item == null)
                        lstDataWhichDoesNotExistsInDb.Add(k);
                    else
                        lstDataWhichExistsInDb.Add(k);
                });

            // now based on ur requirement u can use which list u want..


        }
    }
    public class Entity
    {
        public string Column1 { get; set; }
        public string Column2 { get; set; }
    }
}