Monday, 28 January 2013

"... and what version of the web application are you running, sir?"

A common, and important, requirement of implementing web applications is to version them. Very often the customer themselves care little for the version, but to the QA and Development teams that support them, it is extremely important. Particularly where version control is employed (a fundamental basic principal of good development) and branches of the application must be developed, whilst continuing to maintain the main code trunk, or where multiple versions of the software are available. 

This post will show you how to detail the names and versions of assemblies that the web app is using in ASP.NET MVC3. 

Basic Requirement

At its most basic form the version of the web app itself should be present somewhere for the user to see, such as the About page. This allows them to report a potential bug and the version of the app it has occured in.

Start Visual Studio 2012 and create a new ASP.NET MVC3 Web Application named MyMVCApplication. The default application structure provides various Controllers and Views. As we want to add the version information to the about page, locate the About() method in the HomeController and add the following code:

The controller identifies the name and location of the current applications assembly, extracts the name and version and places the details in the ViewBag ready for the View to display.

The About View needs to display the Assembly and Version stored in the ViewBag:

Now build and run the application, navigate to the About page and, voila, the current version is displayed.


We're using ASP.NET MVC3 here, so we know that this isn't the only assembly being used! The Views are using Razor to output the content of the ViewBag for a start - and Razor resides in its own assembly: System.Web.Razor. It might be useful to list all the assemblies used by the web app in the About page. After all, the more information relating to the version and a reported bug, the simpler it is to locate and fix.
So, lets take the example above a little further to display all the assemblies.

The About controller will need tweaking to discover all the assemblies used and to store the name and version ready for display on the View. We'll define a string dictionary to store the name and version of each assembly as a key value pair, store the dictionary in the ViewBag and call the View.

The About view must also cater for multiple assemblies. We'll simply iterate over the ViewBags' Assemblies property, and output the name (key) and version (value) onto the page.

Build and run the application, navigate to the About page and, voila, all the assemblies currently used in the web app are displayed.

Written by Dan Hacker, Software Developer, DSCallards

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