I am stuck with this problems for a long time now.

Everything I try to do is insert a row in my DB if it's new information - if not update the existing one.

I've updated many entities in my life before - but what's wrong with this code is beyond me (probably something pretty basic) I guess I can't see the wood for the trees...

private Models.databaseDataContext db = new Models.databaseDataContext();

internal void StoreInformations(IEnumerable<EntityType> iEnumerable)
{
 foreach (EntityType item in iEnumerable)
 {
  EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault();
  if (type == null)
  {
   db.EntityType.InsertOnSubmit(item);
  }
  else
  {
   type.Date = item.Date;
   type.LastUpdate = DateTime.Now();
   type.End = item.End;
  }       
 }
}

internal void Save()
{
 db.SubmitChanges();
}

Edit: just checked the ChangeSet, there are no updates only inserts. For now I've settled with

foreach (EntityType item in iEnumerable)
{
    EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault();
    if (type != null)
    {
        db.Exams.DeleteOnSubmit(type);
    }
    db.EntityType.InsertOnSubmit(item);
}

but I'd love to do updates and lose these unnecessary delete statements.