returning an ID when saving a new object

Guest · **Posted:** Wed May 18, 2005 8:03 am

How do I return an ID when saving a new object.

e.g. contentId = dbMgr.Save(myContent);

where contentId is the newly created primary key of the saved content.

lamb.jim · **Joined:** Fri May 13, 2005 1:59 pm **Posts:** 11

Assuming you are using an identity column (auto-incrementing) as you primary key, after calling Save, your object's ID member will be set to the value of the identity column for the newly inserted row.

e.g.

Code:

dbMgr.Save(myContent);
contentId = myContent.Id;

sergey · **Posted:** Wed May 18, 2005 9:20 am

ISession.Save also returns the new object's id.

Guest · **Posted:** Wed May 18, 2005 9:48 am

thx to you both

KPixel · **Posted:** Wed May 18, 2005 10:08 am

If you use SaveOrUpdate(), you have to extract it from the entity:

Code:

myEntity = mySession.SaveOrUpdate(myEntity);
return myEntity.ID;

You should take the entity returned by mySession because, if they are in different AppDomains (happens when using Remoting/WebService) the first entity will not be the updated one (and its ID will still be 0).

srimedia · **Posted:** Mon May 23, 2005 1:06 pm

Hi there,

We're trying to use it this way, but for some reason when we do:

Code:

myContent = new Content();
dbMgr.saveContent(myContent);
iRecId = myContent.ContentId;

...we are getting back a myContent.ContentId of 0.

We have also tried explicitly returning an int from the dbMgr.SaveContent(mycontent), and using:

Code:

myContent = new Content();
iRecId = dbMgr.saveContent(myContent);

...but this results also in a 0 being returned. The database table is auto-incrementing using an identity and a primary key (it is SQL Server 2000).

srimedia · **Posted:** Mon May 23, 2005 1:27 pm

Hm, it's something we're doing wrong. This code:

Code:

public void saveContent(Content c)
      {
         ISession session = null;
         ITransaction tx = null;
         try
         {
            session = factory.OpenSession();
            tx = session.BeginTransaction();
            session.SaveOrUpdate(c);
            tx.Commit();
            session.Close();
         }
         catch (Exception ex)
         {
            tx.Rollback();
            // handle exception
            System.Diagnostics.Debug.WriteLine("exception: " + ex);
         }
         finally
         {
            session.Close();
         }
      }

results in an exception being thrown:

"could not synchronize database state with session"

We must be screwing up our class mappings or something?

sergey · **Posted:** Tue May 24, 2005 3:37 am

srimedia, can you post the mapping of the Content class? And the dbMgr.saveContent method too.

Also, it's impossible to tell what the problem is from that exception. Inner exceptions contain all the useful information.

srimedia · **Posted:** Tue May 24, 2005 7:24 am

Hi Sergey, here is the SaveContent code,

Code:

public void saveContent(Content c)
      {
         ISession session = null;
         ITransaction tx = null;
         try
         {
         session = factory.OpenSession();
         tx = session.BeginTransaction();
         session.SaveOrUpdate(c);
         tx.Commit();
         session.Close();
                      }
         catch (Exception ex)
         {
            tx.Rollback();
            // handle exception
            System.Diagnostics.Debug.WriteLine("exception: " + ex);
         }
         finally
         {
            session.Close();
         }
      }

And here is the mapping code...

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
   <class name="MyProject.Content, MyProject" table="content">
      <id name="ContentId" column="content_id" type="Int32" unsaved-value="-1">
         <generator class="native" />
      </id>
      <property name="Title" column="title" />
      <property name="Summary" column="summary" />
      <property name="StartDate" column="start_date" />
      <property name="EndDate" column="end_date" />
      <property name="Active" column="active" />
      <property name="ContentTypeId" column="content_type_id" />
      <bag name="Links">
      <key column="content_id"/>
      <one-to-many class="MyProject.Link, MyProject"/>
      </bag>
      <bag name="Images" table="image">
      <key column="image_id"/>
      <composite-element class="MyProject.Image, MyProject">
      <property name="Filename" column="filename" />
      <property name="Title" column="title"/>
      </composite-element>
      </bag>
      <bag name="ContentTexts">
      <key column="content_id"/>
      <one-to-many class="MyProject.ContentText, MyProject"/>
      </bag>
      
      
   </class>
   

</hibernate-mapping>

And the inner exception is
{"SQL update or deletion failed (row not found)" }

Thanks for your help!

sergey · **Posted:** Tue May 24, 2005 8:21 am

Well, you have unsaved-value specified as "-1", but from your previous posts it looks like you are using 0 by default. Try initializing the ContentId to -1 in the Content class and see what happens.

(By the way, you don't really have to use SaveOrUpdate, Save should work just fine.)

srimedia · **Posted:** Tue May 24, 2005 11:26 am

Hey, Sergey,

Thanks a lot for your help, that did the trick!

We've seen quite a few different things about Save, Update, and SaveOrUpdate, we'll take a crack with just using Save. Is there any advantage to this other than less typing?

Greets from London,
srimedia

sergey · **Posted:** Tue May 24, 2005 1:43 pm

SaveOrUpdate does either Save or Update :) depending on the unsaved-value of identifier (and possibly version). It's useful when you don't know which method to call and want to let NHibernate decide.

srimedia · **Posted:** Thu May 26, 2005 7:00 am

Heheheh. :D Ok, we should continue to use SaveOrUpdate in that code then, it's not apparent from the context of what we gave you but we are using that code for both Save and Update functionality.

Thanks very much again for your help with this,
srimedia