c# - EntityKey 属性只能在属性的当前值为 null 时设置

Question

我正在尝试以下列方式执行 EF 更新，但继续收到此错误:

只有当属性的当前值为 null 时，才能设置 EntityKey 属性。

        using (hydraEntities db = new hydraEntities())
        {
            YouUser = db.youusers.Include("address").Include("entity").Include("youusercontacts.contact").Include("youuserlogins").Include("youusernotes.note").Include("youusernotes.youuser.entity").Where( yu => yu.YOUUserId.Equals(YOUUserId)).First();
        }

            YouUser.entity.FirstName = txtFirstName.Text;
            YouUser.entity.LastName = txtLastName.Text;
            YouUser.address.AddressLine1 = txtAddressLine1.Text;
            YouUser.address.AddressLine2 = txtAddressLine2.Text;
            YouUser.address.City = txtCity.Text;
            YouUser.address.State = ddlState.SelectedValue;
            YouUser.address.Zipcode = txtZipcode.Text;

            using (hydraEntities db = new hydraEntities())
            {
                db.youusers.AddObject(YouUser);
                db.ObjectStateManager.ChangeObjectState(YouUser, System.Data.EntityState.Modified);
                db.SaveChanges();
            }

非常感谢任何有关如何解决此问题并执行上述语句的见解。

Answer 1

在这种情况下不要使用 AddObject。它用于插入新实体，但您正在更新现有实体。使用 Attach 代替:

using (hydraEntities db = new hydraEntities())
{
    db.youusers.Attach(YouUser);
    db.ObjectStateManager.ChangeObjectState(YouUser, System.Data.EntityState.Modified);
    db.SaveChanges();
}