检查null或空字符串后，实体框架代码首先为null引用异常

Question

我得到了一个空的引用表示，并且无法弄清楚为什么会发生这种情况。只有当我添加LoanTeamMemberNameFunder属性时才会发生这种情况。我有大约50个其他属性，这不会发生。我在设置属性之前检查字符串是空还是空，然后如果是，则分配给null，但仍然得到异常。我还能做些什么来尝试解决这个问题？

[MaxLength(128)]
  public string LoanTeamMemberNameFunder { get; set; }




  MyContext db = new MyContext();

        int i = 0;

        try
        {
            foreach (LoanReportData data in cur)
            {
                Loan loan = new Loan();
                loan.Id = (data["Guid"] == String.Empty ? null : data["Guid"].ToString());
                loan.LoanTeamMemberNameFunder = String.IsNullOrEmpty(data["fields.LoanTeamMember.Name.Funder"].ToString()) ? null : data["fields.LoanTeamMember.Name.Funder"].ToString();



                db.Set<Loan>().AddOrUpdate(loan);

                if ((i % 100 == 0))
                {

                    db.SaveChanges();

                    Console.WriteLine("Total of " + i + " loans updated");
                }

                i++;
            }
        }
        catch (Exception ex)
        {
            db.SaveChanges();
            Console.WriteLine(ex);
        }



        db.SaveChanges();
        db.Dispose();

    }
}

}