i have a two list
List SentList; List MsgList;
both have the same property called MsgID;
MsgList
You can do like this,this is the quickest process
Var result = MsgList.Except(MsgList.Where(o => SentList.Select(s => s.MsgID).ToList().Contains(o.MsgID))).ToList();
This will give you expected output.