只有当属性的当前值为null时,才能设置EntityKey属性

Question

我试图以下列方式执行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();
            }

非常感谢我如何解决这个问题并执行上述声明.

Answer 1

不要AddObject在这种情况下使用.它用于插入新实体,但您正在更新现有实体.Attach改为使用:

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