Question

我正在尝试使用Entity Framework 4.1 Code第一种方法更新实体。我使用以下代码：

public void UpdatePersonEmail(long registryID, string Email) {
            var Person = context.Persons.FirstOrDefault(p => p.RegistryID == registryID);
          //  Person = person;
            Person.Email = Email;
            try
            {
                context.Persons.Attach(Person);
                context.Entry(Person).State = System.Data.EntityState.Modified;
                context.SaveChanges();
            }
            catch (DbEntityValidationException dbEx)
            {
                foreach (var validationErrors in dbEx.EntityValidationErrors)
                {
                    foreach (var validationError in validationErrors.ValidationErrors)
                    {
                        Trace.TraceInformation("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage);
                    }
                }
            }
        }

代码没有给出任何错误，但实体未更新。我只是想更新电子邮件地址。

请建议我解决。

Answer 1

每次执行FirstOrDefault时，都应检查以确保实体不为null。试试这个：

public void UpdatePersonEmail(long registryID, string Email) 
{
    var person = context.Persons.FirstOrDefault(p => p.RegistryID == registryID);
    try
    {
        person.Email = Email;
        context.SaveChanges();
    }
    catch (DbEntityValidationException dbEx)
    {
        foreach (var validationErrors in dbEx.EntityValidationErrors)
        {
            foreach (var validationError in validationErrors.ValidationErrors)
            {
                Trace.TraceInformation("Property: {0} Error: {1}", 
                    validationError.PropertyName, validationError.ErrorMessage);
            }
        }
    }
    catch (NullReferenceException nrEx)
    {
        Trace.TraceInformation("person was null.");
    }
}

使用Entity Framework 4.1更新实体

1 个答案: