converting string into decimal in sum linq query asp.net

public List<total> gettotal(int apid)
    {
        var query = (from a in DB.TblApplicantInstallments
                     where
                         a.ApplicantId == apid
                     group a by a.ApplicantId into g
                     select new total()
                         {
                             paidtotal = g.Where(x => x.Status == "Paid").Sum(x =>decimal.Parse(x.InstallmentDueAmount)),
                            unpaidtoal = g.Where(x => x.Status == "Not Paid").Sum(x => (decimal)x.InstallmentDueAmount)

                         }).ToList();
        List<total> list = query.ToList();
        return list;
           }
}
public class total
{
    public decimal? paidtotal { get; set; }
    public decimal? unpaidtoal { get; set; }
}