删除计时器作业时，它将引发错误“对象引用未设置为对象的实例”

Question

I have created a timer job with following code:

namespace EmployeeDemo
{
    class DeleteEmployees : SPJobDefinition
    {
        public DeleteEmployees() : base() { }

        public DeleteEmployees(string jobName, SPWebApplication webapp)
            : base(jobName, webapp, null, SPJobLockType.ContentDatabase)
        {
            this.Title = "Delete Employees Timer Job";
        }

        public override void Execute(Guid targetInstanceId)
        {
            // Code
        }
    }
}

I then created a Site scoped feature. In its event receiver, on deactivation, I have the following code:

const string timerJobName = "Delete Employees Timer Job";
public override void FeatureDeactivating(SPFeatureReceiverProperties properties)
{
    DeleteJob(properties.Feature.Parent as SPSite);
}
private void DeleteJob(SPSite site)
{
    foreach (SPJobDefinition job in site.WebApplication.JobDefinitions)
    {
        if (job.Name == timerJobName)
        {
            job.Delete();
        }
    }
}

But it throws me error. From debugging I understand that the error is thrown on the line job.Delete(); . The error is:

Object reference not set to an instance of an object.

This is kind of confusing to me as the statement job.Name executes flawlessly and even gets me the right timer job object. But while trying to delete the job it throws me error.

I found this question with similar problem as mine but the suggestions didn't not work for me. From this discussion I tried by writing deletion code in SPSecurity.RunWithElevatedPrivileges but it still didn't work for me.

Anyone knows why this happens and how to resolve this?

Update 1

A little more details.

NullReferenceException was unhandled by user code

Object reference not set to an instance of an object.

Here's the stack trace

   at Microsoft.SharePoint.Administration.SPConfigurationDatabase.DeleteObject(Guid id)
   at Microsoft.SharePoint.Administration.SPConfigurationDatabase.Microsoft.SharePoint.Administration.ISPPersistedStoreProvider.DeleteObject(SPPersistedObject persistedObject)
   at Microsoft.SharePoint.Administration.SPPersistedObject.Delete()
   at Microsoft.SharePoint.Administration.SPJobDefinition.Delete()
   at EmployeeDemo.Features.DeleteEmpFeature.DeleteEmpFeatureEventReceiver.DeleteJob(SPSite site)
   at EmployeeDemo.Features.DeleteEmpFeature.DeleteEmpFeatureEventReceiver.FeatureDeactivating(SPFeatureReceiverProperties properties)
   at Microsoft.SharePoint.SPFeature.DoActivationCallout(Boolean fActivate, Boolean fForce)

Answer 1

To delete the job use powershell:

$jobToDelete = Get-SPTimerJob -WebApplication "http://intranet" -Identity "YourJobName"
$jobToDelete.Delete()

then run:

iisreset /noforce

In the configuration database you need to grant those permission to let deletion work:

use [Sharepoint_Config]
GO
GRANT EXECUTE ON [dbo].[proc_putObjectTVP] TO [WSS_Content_Application_Pools]
GRANT EXECUTE ON [dbo].[proc_putObject] TO [WSS_Content_Application_Pools]
GRANT EXECUTE ON [dbo].[proc_putDependency] TO [WSS_Content_Application_Pools]
GRANT EXECUTE ON [dbo].[proc_putClass] TO [WSS_Content_Application_Pools]
GRANT EXECUTE ON [dbo].[proc_getNewObjects] TO [WSS_Content_Application_Pools]
GRANT EXECUTE ON [dbo].[proc_dropObject] TO [WSS_Content_Application_Pools]
GO