I am very new to RavenDB. 

When I call `SaveChanges()` on my session it executes successfully but the data is not getting stored in the DB.

My code is as follows:

```
using (var session = RavenDocumentStore.OpenSession())
{
    var time = session.Query<Exampleusers>()
            .Where(x => x.Username == userName).FirstOrDefault();
    var temp = time.Id;
    var data = session.Load<Exampleusers>(
            string.Format("Exampleusers/{0}", temp));

    data.Expiration = DateTime.Now;

    session.SaveChanges();
}

```

What is causing the problem?