Upgrade .Net Framework 2.0 To 4.5

Question

I have upgraded my asp.net 2.0 project to 4.5 by using Visual Studio 2012. It is building fine, but will I have to test each webform in the browser or will it be converted 100% automatically? Without the .Net Framework 2.0, will the converted project work fine?

Answer 1

If you had upgraded to 3.5 you would be fine since 3.5 simply built on top of 2.0. NET 4.5 is not a perfect superset of 2.0. There are some differences and without seeing ALL of your code no one, not even Jon Skeet, could tell you if the conversion will "work fine".

I would suggest studying this MSDN article to try and figure out what might have been affected in your upgrade, if anything, and then focusing your testing. Such an approach might actually be more effective than a page-by-page test which would inevitably miss something. It is also possible that the changes from 2.0 to 4.5 might not affect your code-base at all. Here is an exhaustive list of changes from 3.5 to 4.0. Pay special attention to the ASP.NET parts, there are many.

From that last link there is actually a sample (probably more) that might have you checking each page individually:

Page parsing

The page parser for ASP.NET Web pages (.aspx files) and user controls (.ascx files) is stricter in ASP.NET 4 than in earlier versions of ASP.NET, and it flags more markup as invalid than in earlier versions.

Examine error messages that are produced when a page runs and fix errors that result from invalid markup.

Since there are markup differences, you should really check each page and control for proper rendering.