Quartz - .NET Core - Null Reference Exception - asp.net-core

Question

I'm trying to implement the Quartz for .NET Core.
At the moment I have the following:
public class Startup
{
**private IScheduler _scheduler { get; set; }//quartz**
public Startup(IConfiguration configuration)
{
Configuration = configuration;
**_scheduler = ConfigureQuartz();//quartz**
}
public IConfiguration Configuration { get; }
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<Context>(options =>
{
options.UseSqlServer(Configuration.GetConnectionString("notebook14"));
});
...
...
...
**#region for Quartz DI
services.AddScoped<Job>();
services.AddSingleton(provider => _scheduler);
#endregion**
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
endpoints.MapRazorPages();
endpoints.MapControllerRoute(
name: "default",
pattern: "{area:exists}/{controller=Home}/{action=Index}/{id?}");
});
}
**#region for Quartz
private IScheduler ConfigureQuartz()
{
NameValueCollection properties = new NameValueCollection()
{
{"quartz.serializer.type","binary"}
};
StdSchedulerFactory factory = new StdSchedulerFactory(properties);
_scheduler = factory.GetScheduler().Result;
_scheduler.Start();
return _scheduler;
}
#endregion**
...and Program.cs because I would like to start a schedule at first deploy and then run the task every day:
public class Program
{
public static void Main(string[] args)
{
var host = CreateHostBuilder(args).Build();
using (var scope = host.Services.CreateScope())
{
var services = scope.ServiceProvider;
UserManager<AppUser> userManager = services.GetRequiredService<UserManager<AppUser>>();
RoleManager<AppRole> roleManager = services.GetRequiredService<RoleManager<AppRole>>();
**IScheduler scheduler = services.GetRequiredService<IScheduler>();
Start.StartSchedule(scheduler);**
Init.AssignAdmin(userManager, roleManager).Wait();
}
host.Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
...and Start.cs, where I have created the job and the trigger :
public class Start
{
public static Context _context { get; set; }
public Start(Context context)
{
_context = context;
}
public async static void StartSchedule(IScheduler _scheduler)
{
IJobDetail job = JobBuilder.Create<Job>().WithIdentity("Generate", "FreeSlots").Build();
ITrigger trigger = TriggerBuilder.Create().WithIdentity("Trigger", "FreeSlots").StartNow()
.WithDailyTimeIntervalSchedule(t=>t.StartingDailyAt(new TimeOfDay(10,59)))
.Build();
await _scheduler.ScheduleJob(job, trigger);
}
}
...and finally, the Job itself:
public class Job : IJob
{
public Task Execute(IJobExecutionContext context)
{
try
{
Console.WriteLine("TRIGGERED!");
List<AppUser> doctors = Start._context.Users.Where(x => x.Type == AppUser.UserType.Doctor).ToList();
DateTime First = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 8, 0, 0);
List<Appointments> appointments = new List<Appointments>()
{
new Appointments(){Date=First, Time=First,Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(1),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(2),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(3),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(4),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(5),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(6),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(7),Status=Appointments.SlotStatus.Free},
new Appointments(){Date=First, Time=First.AddHours(8),Status=Appointments.SlotStatus.Free},
};
foreach (AppUser doc in doctors)
{
foreach (Appointments slot in appointments)
{
slot.DoctorId = doc.Id;
Start._context.Appointments.Add(slot);
Start._context.SaveChanges();
var message = "Slot for " + slot.DoctorId.ToString() + " " + slot.Time + " " + slot.Status;
Console.WriteLine(message);
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
return Task.CompletedTask;
}
}
The problem is that I get a null reference exception when the Job is executed:
Does anybody have any ideas? Is there a way to make this work? Thank you in advance!