How to compare excel data to SQL and remove duplicate record Using Linq

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C#

C#4.0

Good Day all, I am having little issue removing duplicate record
First I want to be able to compare the record from excel to that of the SQL, if the same, one will be deleted.. How do i please achieve that below is the code on how to import to sql using linq

            try
            {
               

                    string Pat = string.Concat(Server.MapPath("~/FileUpload/" + FileUpload1.FileName));
                    FileUpload1.SaveAs(Pat);
                    string PathToExcelFile = Pat;
                    var ExcelFile = new ExcelQueryFactory(PathToExcelFile);
                    
                    ExcelFile.AddMapping<Question>(x => x.QuestionOrder, "QuestionNo");
                    ExcelFile.AddMapping<Question>(x => x.Title, "Question");
                    ExcelFile.AddMapping<Question>(x => x.Answer1, "A");               

                    ExcelFile.TrimSpaces = LinqToExcel.Query.TrimSpacesType.Both;
                    ExcelFile.ReadOnly = true;
                    IQueryable<Question> Quest = (from c in ExcelFile.Worksheet<Question>() select c);
                    foreach (Question qu in Quest)
                    {
                        cdc.Questions.Add(qu);
                        cdc.SaveChanges();
lblmess.Text = "Imported Successfully";

                    }
               
            }
            catch(Exception ex)
            {
                lblmess.Text = ex.Message;
            }

Thank you very much.. I really do appreciate your time and effort.