Databases
StackOverflow2013
Postsdbo
POEntity Framework - Saving child entities
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POEntity Framework - Saving child entities
    primarykey
    data
    text
    <p>I'm using EF and WebAPI and trying to save a new object that has many child properties (eg city, country, etc). The data for these properties is pulled from an external source but I want to save them to my database along with my object for reporting purposes. For that reason I need to first check if the new child being passed along with the new parent already exists (remember, it's not being pulled from my database). </p> <p>If I've selected, for example, a city I've already saved, it saves a duplicate row because the object passed in doesn't have MY city ID so EF thinks it's a new item.</p> <p>I've tried attaching if it is already in the DB but it won't let me attach. It says the item is already being tracked by the context. </p> <p>Here is my code for trying to check and save one of the child collections before saving the new parent.</p> <pre><code>foreach (HBCountry country in hbcampaign.HBTargetingSpec.HBCountries) { if (db.HBCountries.Any(c =&gt; c.country_code == country.country_code)) { country.CountryID = db.HBCountries.Where(c =&gt; c.country_code == country.country_code) .FirstOrDefault() .CountryID; db.HBCountries.Attach(country); } else { db.HBCountries.Add(country); } } </code></pre> <p>I need to grab the ID of the existing entity from my context but after that I can't attach and let EF know that it doesn't need to create a new entry for this item. </p> <p>I'm pretty new to EF and I'm constantly struggling with saving / updating any entities that have child collections. I can't seem to wrap my mind around when things are attached to the context and when not etc. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USGooseZA
    1. USGooseZA
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COYou're attaching already tracked entity. Just get the parent and either use parent.Childern.Add() or parent.ChildernId = id to add child entity. I hope you're not using Lazy Loading here.
      singulars
      1. POEntity Framework - Saving child entities
      1. USMatija Grcic
    2. COIt is better to use `Any()` than `Count() > 0`. `Count()` loop through the whole collection, `Any()` without a predicate just peeks at the first item and returns.
      singulars
      1. POEntity Framework - Saving child entities
      1. USOndrej Janacek
    3. COThanks. I've updated my code to use Any(). I'm still stuck though. If I was pulling the child properties from my own data source this wouldn't be as big a problem but because I'm basically sending in a "new" item each time (ie it doesn't have an ID from my DB yet). Sorry if this is very silly. I'm really struggling to get to grips with EF.
      singulars
      1. POEntity Framework - Saving child entities
      1. USGooseZA
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload