How to create Scheduled Jobs in .net web applications.
Calling a function at predefined iteration of time has been one of the key requirements of web applications.
Example:
You want to automatically archive the data.
You want to automatically purge the data.
You want to automatically send the News Letters.
You want to take backup of the files or database etc.
Generally this type of functionality can be easily archived by creating and configuring scheduled jobs in SQL Server.
What if you are using the express edition of SQL Server?
You cannot take advantage of this feature because all the editions of SQL Server do not provide this functionality.
In this article I will explain how we can achieve this functionality using purely .Net framework class.
First of all let’s thanks System.Threading class. The main cream lies inside this class shipped in .Net Framework. Many of us usually do not use it but believe me its one of the most beautiful classes of the framework.
Anyways
Following are the steps which you need to perform:
Step 1) Create a class called Jobs.cs
namespace myScheduler
{
public sealed class Jobs
{
public Jobs(){}
public static void DailyJob(object state)
{
//Your dream goes here.
}
public static void HourlyJob(object state)
{
//Your dream goes here.
}
}
}
Jobs class includes the below two functions that will be called by our scheduler which we will create in the second step.
I have created two functions for this purpose.
DailyJob: Will be called daily by the scheduler.
HourlyJob: Will be called hourly by the scheduler.
Step 2) Create a class called Scheduler.cs
using System;
using System.Threading;
namespace myScheduler
{
public sealed class Scheduler
{
public Scheduler() { }
public void Scheduler_Start()
{
TimerCallback callbackDaily = new TimerCallback(Jobs.DailyJob);
Timer dailyTimer = new Timer(callbackDaily, null, TimeSpan.Zero, TimeSpan.FromHours(24.0));
TimerCallback callbackHourly = new TimerCallback(Jobs.HourlyJob);
Timer hourlyTimer = new Timer(callbackHourly, null, TimeSpan.Zero, TimeSpan.FromHours(1.0));
}
}
}
Scheduler class contains the actual mechanism for running jobs created in Jobs class in Step one.
Timer: Mechanism for executing method at specified time intervals. This method has 5 overloads which we can use as per our needs. Some of its parameters are
TimerCallback: Represents the method that you want to actually callback on at a particular interval of time.
State: Any type of object you want to pass to your callback method.
Due Time: Amount of delay after which callback will be invoked. TimeSpan.Zero means immediately.
Period: Time period between invocations of callback function.
Step 3) Add Global.asax file to your web project. In Application_Start event instantiate Scheduler object and make a call to Scheduler_Start() method.
<%@ Application Language="C#" %>
<%@ Import Namespace="myScheduler" %>
<script RunAt="server">
void Application_Start(object sender, EventArgs e)
{
// Code that runs on application startup
Scheduler objmyScheduler = new Scheduler();
objmyScheduler.Scheduler_Start();
}
void Application_End(object sender, EventArgs e)
{
// Code that runs on application shutdown
}
void Application_Error(object sender, EventArgs e)
{
// Code that runs when an unhandled error occurs
}
void Session_Start(object sender, EventArgs e)
{
// Code that runs when a new session is started
}
void Session_End(object sender, EventArgs e)
{
// Code that runs when a session ends.
// Note: The Session_End event is raised only when the sessionstate mode
// is set to InProc in the Web.config file. If session mode is set to StateServer
// or SQLServer, the event is not raised.
}
</script>
You are done.
How it works?
Whenever the applications is first started the Application_Start() in Global.asax is called and this calls Scheduler_Start() method which configures all the Jobs that we have created.
I have demonstrated a daily and hourly job in the above examples. In order to debug and test this code you need to wait for an Hour or a Day. Don’t panic I have done this intentionally. So in order to brush up your above learning’s prepare a job in Jobs.cs file that would be called every minute. Configure the callback and timer for your new job in Scheduler.cs file and enjoy the gist of scheduling.
Note: After running the project once do not forget to restart the IIS because Application_Start() wont be called every time you run your project. You know why?
