.NET implementation of the SynchronizerToken pattern

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Introduction

Joe was doing online shopping, he clicked the Submit button to place an order, there was no response for 5 seconds, he thought something had gone wrong and clicked the button again!

What happened?

Joe probably got charged twice!! It was only because he could not receive the response for whatever reason, but the sever got two requests from him and placed duplicate orders for him.

Here is a solution which can prevent such kind of mistakes.

Background

Basically, this is a .NET implementation of the SynchronizerToken pattern which has been used in the Java world for years (refer to Core J2EE Patterns).

Using the code

It is pretty easy to use:

1. add a reference to the SynchronizerToken assembly in your project.
2. inherit you page from the Synchronizer page.
3. add the [OneSubmitOnly] attribute right before your page class.

// Default message will be shown when duplicated
// submission happened if no RedirectURL property set. 
//[OneSubmitOnly]
// Request will be redirected to ErrorPaga.aspx
// when duplicated submission happened. 
[OneSubmitOnly(RedirectURL = "~/ErrorPage.aspx")] 
public class WebForm1 : Synchronizer 
{
  .......
}

Points of Interest

1. The OneSumbmitOnly attribute has an optional RedirectURL property which points to any valid URL to where a request gets redirected when duplicated submission happens. If no RedirectURL property is set, the request gets rejected and the default message will show up.
2. Resubmission is checked before any subclass event.

History

• Version: 1.0
  • Creation date: 2005-09-30
• Version: 1.1
  • Modified date: 2005-10-5

    Found a way to make resubmission check happen before any subclass event happens by overriding the OnLoad event handler. Now there is no worry about silly things happening in the subclass' Page_OnLoad method before the resubmission check.