I have created a very simple sharepoint timer job. All i want it to do is iterate through a list and update each list item so that it triggers an existing workflow that works fine. In other words all i am trying to do is work around the limitation that workflows cannot be triggered on a scheduled basis. I have written a class that inherits from SPJobDefinition that does the work and i have a class that inherits from SPFeatureReceiver to install and activate it. I have created the feature using SPVisualdev that my coleagues have used in the past for other SP development.

My Job class is below:

public class DriverSafetyCheckTrigger : SPJobDefinition
{
    private string pi_SiteUrl;
    public DriverSafetyCheckTrigger(string SiteURL, SPWebApplication WebApp):base("DriverSafetyCheckTrigger",WebApp,null, SPJobLockType.Job)
    {            
        this.Title = "DriverSafetyCheckTrigger";
        pi_SiteUrl = SiteURL;            
    }

    public override void Execute(Guid targetInstanceId)
    {
        using (SPSite siteCollection = new SPSite(pi_SiteUrl))
        {
            using (SPWeb site = siteCollection.RootWeb)
            {
                SPList taskList = site.Lists["Driver Safety Check"];
                foreach(SPListItem item in taskList.Items)
                {
                    item.Update();                        
                }
            }
        } 
    }
}

And the only thing in the feature reciever class is that i have overridden the FeatureActivated method below:

public override void FeatureActivated(SPFeatureReceiverProperties Properties)
    {
        SPSite site = Properties.Feature.Parent as SPSite;

        // Make sure the job isn't already registered.
        foreach (SPJobDefinition job in site.WebApplication.JobDefinitions)
        {
            if (job.Name == "DriverSafetyCheckTrigger")
                job.Delete();
        }

        // Install the job.
        DriverSafetyCheckTrigger oDriverSafetyCheckTrigger = new DriverSafetyCheckTrigger(site.Url, site.WebApplication);

        SPDailySchedule oSchedule = new SPDailySchedule();
        oSchedule.BeginHour = 1;

        oDriverSafetyCheckTrigger.Schedule = oSchedule;

        oDriverSafetyCheckTrigger.Update();
    }

The problem i have is that when i try to activate the feature it throws a NullReferenceException on the line oDriverSafetyCheckTrigger.Update(). I am not sure what is null in this case, the example i have followed for this is this tutorial. I am not sure what I am doing wrong.