PRG Design Pattern

PRG stands for Post-Redirect-Get, a web development design pattern which targets to avoid duplicate form submissions because of refreshing the web page.

Currently, in most of the modern browsers, when we refresh the web page right after we submit a form in the page, we will receive a confirmation alert box asking if we confirm want to re-submit the same form.

This can happen in an e-commerce website. If the customer accidentally pressed “Continue” button on the box to proceed, then there may be a duplicate online purchase. The confirmation box is good but it does not remove the risk of form re-submission.

To avoid all these issues, PRG web design pattern is introduced.

PRG and ASP .NET Web Form

In ASP .NET Web Form context, instead of returning a web page direct, we will do a Response.Redirect (302 Redirect) to a confirmation page (or redirect back to the original same page) first. So now user can safely refresh the result page without causing the form re-submission.

By using PRG design pattern, we will thus need to store the data somewhere so that the two web pages can communicate. For example, if we want to show the Receipt Order Number generated after the POST in the confirmation page, then we can store the number in Session variable.

PRG and ASP .NET MVC

In ASP .NET MVC, instead of using Response.Redirect, we will be using RedirectToAction. Then we will store the data in TempData for the next page to consume, for example.

Thoughts about PRG

PRG design patter is not good for every case having form submission involved. For example, if we have a report module that user can search by providing start date and end date, then it is fine to have form re-submission with every page refresh.

Summer 2015 Self-Learning Project

This article is part of my Self-Learning in this summer. To read the other topics in this project, please click here to visit the project overview page.