如何更新实体框架子列表？ [英] How to update child list in entity framework?

问题描述

这些机型：

public class Contact
{
    public Contact() 
    {
        Emails = new List<Email>(); 
    }
    public int Id { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
    public string Address { get; set; }
    public ICollection<Email> Emails { get; set; }

}
 public  class Email
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual int ContactId { get; set; }
}

在我的详情页面用户可以添加更多的电子邮件，删除exsting ...等...或更改现有之一。
如何更新收藏？
我会尝试这样的：

On my details page user is able to add more emails, delete exsting...etc...or change existing one. How to update collection? I tries this:

    var contactFromDb = db.Contacts.Include("Emails").Include("Telephones").Where(x => x.Id == contact.Id).FirstOrDefault();

      contactFromDb.Address = contact.Address;
      contactFromDb.Name = contact.Name;
      contactFromDb.Surname = contact.Surname;
      contactFromDb.Telephones = contact.Telephones;
      contactFromDb.Emails = contact.Emails;

字符串性能是很好的更新，我试图更新集合以同样的方式，但我得到重复的值。如何更新电子邮件？

String properties are updated nicely, I tried updating collection the same way, but I get duplicate values. How to update emails?

推荐答案

首先删除电子邮件去掉：

First delete removed emails:

var contactFromDb = db.Contacts.Include("Emails").Include("Telephones").FirstOrDefault(x => x.Id == updatedContact.Id);
contactFromDb.Address = updatedContact.Address;
contactFromDb.Name = updatedContact.Name;
contactFromDb.Surname = updatedContact.Surname;

// Delete removed emails
var emailsToDelete = (from email in contactFromDb.Emails
                        let item = updatedContact.Emails.SingleOrDefault(i => i.Id == email.Id)
                        where item == null
                        select email).ToList();
if (emailsToDelete.Any())
{
    foreach (var email in emailsToDelete)
    {
        db.Entry(email).State = EntityState.Deleted;
    }
}

这是更新编辑电子邮件后：

After that update edited emails:

foreach (var email in updatedContact.Emails)
{
    // If id of an email is not equal to 0, it's not new email and it should be updated
    if (email.Id > 0)
    {
        var emailInDb = contactFromDb.Emails.Single(e => e.Id == email.Id);
        db.Entry(emailInDb).CurrentValues.SetValues(email);
        db.Entry(emailInDb).State = EntityState.Modified;
    }
}

最后通过调用 db.SaveChanges（）与标识新邮件 0 将被插入，你可以重复这个周期电话。

And finally by calling db.SaveChanges() new emails with Id of 0 Will be inserted and you can repeat this cycle for Phones.

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