How to create Scheduled Jobs in .net web applications.

30 08 2008

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?

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How to Encrypt or Decrypt sections of Configuration file.

15 08 2008

How to Encrypt or Decrypt sections of Configuration file.

It is always a good practice to protect sensitive information in configuration files. One should always protect connectionStrings section from being easily readable; also some times it becomes necessary to encrypt appSettings section that may include some sensitive data. You know why…?

So in this Blog I will walkthrough the steps required for encryption\decryption of sections in configuration file.

.Net framework ships two providers for this purpose.
RsaProtectedConfigurationProvider and DpapiProtectedConfigurationProvider.
Here I will use RsaProtectedConfigurationProvider.

 
Step 1) First off all we will add provider to configuration section of web.config file that you want to play with. This provider is required for actual processing done while running commands depicted in step 3 and 4.


<configuration>
<configProtectedData defaultProvider="myProvider">
<providers>
 <clear/>
  <add name="myProvider"
  type="System.Configuration.RsaProtectedConfigurationProvider"
  keyContainerName="NetFrameworkConfigurationKey"/>
</providers>
</configProtectedData>
</configuration>

 RsaProtectedConfigurationProvider requires key container for encryption and decryption purpose. This container includes private\public keys that are required during encryption and decryption process by the attached provider.

NetFrameworkConfigurationKey : This is the default key container shipped by Microsoft. You can also create your own key container that includes private\public keys required for encryption\decryption. In order to avoid confusion I will depict these steps in my next article.

Note: As we are using default key container “NetFrameworkConfigurationKey” you can do away with the first step. This step will be added by machine.config file cause it includes declaration for both providers  (“RsaProtectedConfigurationProvider” and “DpapiProtectedConfigurationProvider”). But this will be helpful incase we are creating our own key container.

Step 2) After adding the provider in Step 1 go to the Visual Studio command prompt. Now In order to access “NetFrameworkConfigurationKey” key container your “ASPNET” account must have permission to access it. Run the below command to give access.

aspnet_regiis -pa “NetFrameworkConfigurationKey” “ASPNET”

 

Step 3) Run below command to encrypt connectionStrings section of your web.config file located in the virtual directory named “MyWebApplication”.

aspnet_regiis -pe connectionStrings -app /MyWebApplication

 

Step 4) Run below command to decrypt connectionStrings section of your web.config file located in the virtual directory named “MyWebApplication”.

aspnet_regiis -pd connectionStrings -app /MyWebApplication

Note: You can replace the “connectionStrings” section with the section name you want to encrypt\decrypt.
Eg: aspnet_regiis -pe appSettings -app /MyWebApplication
This will encrypt “appSettings” section of your web.config file located in the virtual directory named “MyWebApplication”.

To get more help about aspnet_regiis use the below command
aspnet_regiis help