Databases
StackOverflow2013
Postsdbo
POLinq to Entities - Reference EntityKey
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POLinq to Entities - Reference EntityKey
    primarykey
    data
    text
    <p>Now that I have built a database. </p> <p>Visual Studio 2008 SP1’s ADO.NET Entity Framework has generated an Entity Model like this: <a href="http://img835.imageshack.us/img835/1810/carease15test1ef.png" rel="nofollow">http://img835.imageshack.us/img835/1810/carease15test1ef.png</a></p> <p>I have created a method as follow:</p> <pre><code> private void buttonAddPatient_Click(object sender, EventArgs e) { using (carease15test1Entities context = new carease15test1Entities()) { long bnumber = Convert.ToInt32(textBoxToBed.Text); long rnumber = Convert.ToInt32(textBoxOfRoom.Text); long bid = (from b in context.bed where b.bnumber == bnumber select b.bid).First(); long rid = (from r in context.room where r.rnumber == rnumber select r.rid).First(); // Create a new bed, and input its details. patient p = new patient(); p.pname = textBoxPatient.Text; p.Bed_bid = bid; p.bedReference.EntityKey = new EntityKey("carease15test1Entities.bed", "bid", bid); p.Bed_Room_rid = rid; p.bed.roomReference.EntityKey = new EntityKey("carease15test1Entities.room", "rid", rid); context.AddTopatient(p); try { context.SaveChanges(); } catch (OptimisticConcurrencyException ex) { // Resolve the concurrency conflict by refreshing the // object context before re-saving changes. context.Refresh(System.Data.Objects.RefreshMode.ClientWins, p); // Save changes. context.SaveChanges(); } catch (Exception ex) { MessageBox.Show(ex.Message); } } } </code></pre> <p>Everything works perfectly except for</p> <p>p.bed.roomReference.EntityKey = new EntityKey("carease15test1Entities.room", "rid", rid);</p> <p>It turns out a NullRefenceException saying “Object reference not set to an instance of an object.”</p> <p>Here is my project files.</p> <p><a href="http://www.mediafire.com/?w3rjjbxbxw6wacv" rel="nofollow">http://www.mediafire.com/?w3rjjbxbxw6wacv</a></p> <p>Could anyone give me some help?</p> <p>Thank you so much.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USPriere Law
    1. USPriere Law
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COpossible duplicate of [What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)
      singulars
      1. POLinq to Entities - Reference EntityKey
      1. USJohn Saunders
 

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