Getting identity column value using entity framework 4.1

Question

I'm using entity framework 4.1 (VS 2010, SQL Server 2012) for inserting data into a database. First I create an instance of an object, fill the properties with values and call AddObject(), like this:

VideoData videodata = new VideoData();
videodata.StartCaptureTime = startCaptureTime;
videodata.EndCaptureTime = endCaptureTime;
videodata.CameraID = CameraID;

using (var context = new PercEntities())
{             
    if (context.VideoDatas.Where(c => c.VideoID == videoID).Count() == 0)
    {
       var videoData = new VideoData
       {
           StartCaptureTime = startCaptureTime,
           EndCaptureTime = endCaptureTime,
           CameraID = CameraID,
       };
    context.VideoDatas.AddObject(videoData);
    context.SaveChanges();
   }
}

The thing is, that the table in the database has an identity column:

VideoID int IDENTITY(1,1)

and I need to get the value inserted by the identity function in order to fill additional objects, that have the VideoID as a foreign key. for example:

FrameData frameData = new FrameData();
frameData.VideoID = videodata.VideoID;
frameData.Path = path;

The only thing I could think of was to query for the max identity right after AddObject(videoData), but I'm afraid of race conditions.

I'm new to Entity Framework, so I'd be happy for any guidance on this.

Answer 1

If you have other objects which require VideoID as FK you just need to correctly configure your navigation properties between VideoData and those other types and EF will handle it for you.

Call to AddObject does not insert your data to database and because of that you cannot get the identity value after this call. Only call to SaveChanges will push all your changes to database and during this call EF will handle referential integrity internally (but only if you have your model correctly configured with relations).

After calling SaveChanges your VideoID should be populated automatically if you have everything correctly configured.