Executing a process periodically in Windows

There are many types of application running in an enterprise. One of it is called the "nightly job" (i.e., the job that runs periodically) which is running on every night. On the other hand, some of the jobs is running hourly, weekly or monthly.

In our experience, the main issue in running a process periodically is that "schedule" itself. Consider this:

• The simplest schedule job - run the job every night.
• Run the job once for every hour, week, month or year.
• Run the job once for every hour, week, month or year between 10AM to 6PM.
• Run the job on every Monday, hourly between 10AM to 6PM.

This is complicated and requires lots of testing if you are creating your scheduler program. Instead, the better way is to utilized the Task Scheduler that comes with Windows. This is what you have paid for.

Below is the screen snapshot of where you can find the Task Scheduler.

Below are a few ways to execute a job/process periodically in Windows:

1. Develop a Windows Service - add a System.Threading.Timer class and execute the callback periodically. With Timer class, it is able to run the process repeated in the same interval. If you want to run the next callback in different timing, you will have to calculate the interval and call Change() which will be complicated (depends on your need). Another problem that might arise is how to include the dependencies (or DLL)? For example, you need to generate daily report in PDF format and email it to the bosses.
2. Develop a program (.EXE) and schedule it in the Windows Task Scheduler - this is simple and clear cut. With this option, it solves the scheduling problem. But, it does not solve the dependencies problem as mentioned above.
3. Develop a web page which execute the process in a different thread and schedule it in the Windows Task scheduler - another requirement for this option is that it requires a small program which will call the URL (using System.Net.HttpWebRequest class) and pass the URL as the command line parameter. This solves the scheduling complexity (which handles by the Windows Task Scheudler) and also the dependencies (where all the business processes/rules are stay in the ASP.NET website). Of course, if the business processes/rules were in the Windows Client EXE, you will have no choice but fall back to strategy #2 as mentioned above.

Reusable custom web control

When you are building web application, blog site, forum, shopping cart, etc, often, there are some information in "div" will be reuse throughout the website or reused in selected pages. To avoid writing the HTML tag again and again, you may consider using the custom web control.

To create custom web control, right click on your web project and choose Add New Item. Then, choose Web User Control (i.e., System.Web.UI.UserControl class). Web user control is able to utilize the HTML designer in Visual Studio. So, you will be able to complete the design in a shorter time.

Another way to create custom control is to writing codes by declaring a new control which inherits from CompositeControl or WebControl. But it does not support any visual designer. The biggest challenge is for the graphic designer to touch up the design in C#/VB.Net code because they are not the programmer.

Advantage of using UserControl:

• Easily separate the JavaScript from the web page.
• Easily moving the control around the web page.
• Easier to test the custom web control.
• Easier to share the same control in different design style with other projects.
• Easier to maintain the design with or without using CSS file.
• Reduce the complication of HTML tags within a page.

When to use it?

• You have to display "modal dialogue" box in the page which requires JQuery dialog. This dialog requires a "div" for the dialog and also contains the many data entry fields.
• The "compulsory" aster rick marker in red color.
• The "last updates", "news" or "events" section.
• The banner for header and footer.
• Application menu.

Should I develop a custom control or just add it to the form

The definition of "reusable control":

• The control will be reused in many areas in the same project - for example, "customer group" drop down list which can be reused in many screens within the same project.
• The control will be used more than once in a project and also useful in other project - for example, DevExpress has developed xtraReport which can be reuse in many projects.
• The control will be used only once in a project and also useful in other project - for example, you have developed a "main menu" control which reads the menu options from XML file.

In order to speed up the development, testing, implementation and maintenance, you are advisable to come out with a custom control and then drag it into other custom control or Form.

Tricks for using custom control:

• Drag the custom control on a MDI child Form - in this case, you control will always sit inside the MDI parent window.
• Drag the same custom control on a non-MDI child Form - in this case, you can shown the control modally.
• Drag the same custom control into a Tab page control and show it in any Form - now, you custom control will be act like a tab page.
• Another rare situation is that you instantiate this custom control at runtime and position it to the appropriate location. By doing this, you don't have to mess up the parent control/Form. The coding will be very clean and precise.