Problems finding JobDefinition in WebApplication-Feature in SharePoint 2010

Question

I got a SharePoint-Feature under the WebApplication-Scope that should create a Timer-Job.

On feature-activation (before creating that Job) and on feature-deaktivation I want to delete the job if it already exists. This is the feature-activation-Code:

public class myJob : SPJobDefinition
  public myJob() : base("JobName", SPAdministrationWebApplication.Local, null, SPJobLockType.Job) {}
}

public class JobFeature : SPFeatureReceiver
{
  public override void FeatureActivated(SPFeatureReceiverProperties properties)
  {
    SPWebApplication application = properties.Feature.Parent as SPWebApplication;
    // 1. Delete old Job if exists
    foreach (SPJobDefinition job in application.JobDefinitions)
    {
      if (string.Equals(job.Name, "JobName"))
      {
        job.Delete();   // NEVER GETS HERE
      }
    }
    // 2. Install job
    myJob deploymentJob = new myJob();
    SPMinuteSchedule schedule = new SPMinuteSchedule { BeginSecond = 0, EndSecond = 59, Interval = 5 };
    deploymentJob.Schedule = schedule;
    deploymentJob.Update(); // CRASHES
  }
}

The Problem is: The code that should delete the job is never reached. The job just does not seem to be in application.JobDefinitions. ("// NEVER GETS HERE" in the code above)

But when I try to create the deploymentjob I got an exception that the job already exists ("// CRASHES" in the code above):

{"An object of the type myJob named \"JobName\" already exists under the parent Microsoft.SharePoint.Administration.SPAdministrationWebApplication named \"\".  Rename your object or delete the existing object."}

Where is the error?

Answer 1

When using another constructor it works...

public myJob(SPWebApplication application)
            : base("JobName", application, null, SPJobLockType.Job)
        {

        }