C#

private void button2_Click(object sender, EventArgs e)
        {
            var before = System.Diagnostics.Process.GetCurrentProcess().VirtualMemorySize64;

            List<string> lst1 = new List<string>();

            for (int i = 0; i <= 1000000; i++)
            {
                lst1.Add("Test Test Test Test Test Test Test Test Test Test Test Test Test Test Test ");
            }

            var after = System.Diagnostics.Process.GetCurrentProcess().VirtualMemorySize64;

            lst1.Clear();
            lst1.TrimExcess();

            var current = System.Diagnostics.Process.GetCurrentProcess().VirtualMemorySize64;
        }

try
            {
                Random rand = new Random();
                await Task.Delay(rand.Next(300, 1000));     //sims clicks
                var webcontent = await task.Crawl().Timeout(timeout);
            }
            catch (CrawlerTimeoutException)
            {
               //do something
               
            }
            catch (Exception exp)
            {
               //do something
            }

CrawlerTimeoutException

task.Crawl().Timeout(timeout);

public static Task<T> Timeout<T>(this Task<T> task, int millisecondsTimeout)
        {
            return Task.Factory.StartNew(() =>
            {
                bool succ = task.Wait(millisecondsTimeout);
                if (succ)
                    return task.Result;
                else
                    throw new CrawlerTimeoutException("Task timeout");//here is the error
            });
        }

When I am Trying to save current list of data into database, I need to get already existing data from database, and need to compare with current list of data.

I have two lists one is PreviousList(existing data from DB) and other is CurrentList(Modified data)


    public class SoftClose
    {
        public int ID = -1;
        public int AID = -1;
        public int WFID = -1;
        public string PREFIX;
        public DateTime SCDATE;
        public string STATUS;
    }


PreviousList
------------
ID		Status		AID		WFID 	PREFIX		SCDATE
1		NO_CHANGE	19		388		D1			01/28/2019
2		NO_CHANGE	20		388		D2			02/25/2019
3		NO_CHANGE	21		388		D3			03/30/2019

CurrentList
-----------
ID		Status		AID		WFID 	PREFIX		SCDATE
1		NO_CHANGE	19		388		D2			01/28/2019
2		NO_CHANGE	20		388		D2			02/25/2019
3		NO_CHANGE	21		388		D3			03/30/2019
4		NO_CHANGE	22		388		D4			04/09/2019


In CurrentList I modified Prefix to D2 where ID=1 and added new row(Id=4)...

My req is

When I am trying to save CurrentList to Db,

If there is any new Prefix in CurrentList that is not there in PreviousList I need to insert that new row and need to change Status to ADD for that row.

I changed Prefix to D2 where Id = 1 in CurrentList. D1 is there is DB and but not in CurrentList so i need to delete it. So i need to change the status to DELETE for that record. I should not insert D2 record where id=1 becuase D2 is already there. If I changed to D5 where Id = 1 then I need to insert it because D5 is not there in DB So i need to change the status to UPDATE.

How to do this? What is the best approach to compare lists