Question

我正在使用以下代码从网络表单收集数据：

secondContact.FirstName = txtFirstNameContact2.Text;
secondContact.LastName = txtlastNameContact2.Text;
secondContact.EmailAddress = txtEmailAddressContact2.Text;
secondContact.PhoneNumber = txtPhone1Contact2.Text + txtPhone2Contact2.Text + txtPhone3Contact2.Text;
if (!string.IsNullOrEmpty(rblContactTypeContact2.SelectedValue))
{
    secondContact.SecondaryContactTypeID = Convert.ToInt32(rblContactTypeContact2.SelectedValue);
}
secondContact.ContactPosition = 2;
secondContact.ProspectID = prospect.Id;

将代码发送到存储库以使用下面的代码保存（它抓住了prospect.Id成功）：

if (prospect.Id != 0)
   {
    if (!string.IsNullOrEmpty(secondContact.FirstName) || !string.IsNullOrEmpty(secondContact.LastName) || !string.IsNullOrEmpty(secondContact.EmailAddress) || !string.IsNullOrEmpty(secondContact.PhoneNumber))
    {
        this.repository.SaveAltContact(prospect.Id, 2, secondContact);
    }
}

存储库尝试保存数据：

public void SaveAltContact(int prospectID, int contactPosition, SecondaryContact contact)
{
    using (var context = new CoyleHomeBuyerEntities())
    {
        SecondaryContact currentAltContact = new Model.SecondaryContact();

        currentAltContact = (from sec in context.SecondaryContact
                             where sec.ContactPosition == contactPosition
                             where sec.ProspectID == prospectID
                             select sec).FirstOrDefault();

        if (currentAltContact == null)
        {
            context.AddToSecondaryContact(currentAltContact);
        }

        currentAltContact.FirstName = contact.FirstName;
        currentAltContact.LastName = contact.LastName;
        currentAltContact.EmailAddress = contact.EmailAddress;
        currentAltContact.PhoneNumber = contact.PhoneNumber;
        currentAltContact.SecondaryContactTypeID = contact.SecondaryContactTypeID;
        currentAltContact.ProspectID = prospectID;
        currentAltContact.ContactPosition = contactPosition;

        context.SaveChanges();
    }
}

在此行之后总是失败并出现Null异常：

context.AddToSecondaryContact(currentAltContact);

我很困惑，因为我希望上面的查询在这一点上返回一个NULL值。 SecondaryContactID被设置为主键并自动递增。

Exception Details: System.ArgumentNullException: Value cannot be null.
Parameter name: entity

在尝试向数据库添加新行时，有人能指出正确的方向吗？

Answer 1

您正在添加null作为记录，当您在数据库中没有记录时，添加contact而不是currentAltContact。当您想要更新记录时，方法AddToSecondaryContact将具有联系对象以添加新记录和currentAltContact。

更改

if (currentAltContact == null)
{
    context.AddToSecondaryContact(currentAltContact);
}

到

if (currentAltContact == null)
{
    context.AddToSecondaryContact(contact);
}

Answer 2

实际上我通过简单地在顶部声明currentAltContact变量并仅在存在空记录时实例化新对象来实现它

public void SaveAltContact(int prospectID, int contactPosition, SecondaryContact contact)
    {
        using (var context = new CoyleHomeBuyerEntities())
        {
                SecondaryContact currentAltContact;

            currentAltContact = (from sec in context.SecondaryContact
                                 where sec.ContactPosition == contactPosition
                                 where sec.ProspectID == prospectID
                                 select sec).FirstOrDefault();

            if (currentAltContact == null)
            {
                currentAltContact = new Model.SecondaryContact();
                context.AddToSecondaryContact(currentAltContact);
            }

            currentAltContact.FirstName = contact.FirstName;
            currentAltContact.LastName = contact.LastName;
            currentAltContact.EmailAddress = contact.EmailAddress;
            currentAltContact.PhoneNumber = contact.PhoneNumber;
            currentAltContact.SecondaryContactTypeID = contact.SecondaryContactTypeID;
            currentAltContact.ProspectID = prospectID;
            currentAltContact.ContactPosition = contactPosition;

            context.SaveChanges();
        }
    }

添加到表时出现Null异常

2 个答案: