in the code I have a method that reads data from an excel sheet and store the record in a list, I want to compare certain columns with the database records if they exist I want to ask the user (take the user conformation with "confirm" in javascript for example) if he wants to replace the new data with the old one or keep the old one, my issue is how can I go to the view to ask the user then go back to continue with my method? or if there is a way to ask the user without going to the view

my controller

 foreach (var n in KPlist)
                {

                    var compare = _db.Kpiprograms.Where(x => x.ProgramId == n.ProgramId && x.Year == n.Year && x.Term == n.Term && x.KpiId == n.KpiId).Any();
                    if (compare)
                    {
                      //am stuck here 
                    }
                 
                }