Will I have any issues if I upgrade from .NET 4.0 to 4.5

just.another.programmer picture just.another.programmer · Nov 24, 2012 · Viewed 17k times · Source

I have an existing web app using a combination of MVC and WebForms on .NET 4.0. I want to upgrade to 4.5 to take advantage of some new features in EF 5 (which require 4.5). A couple of questions to hopefully prevent breaking the live site:

  1. When I install .NET 4.5 to the hosting server, will it supercede 4.0, or will my 4.0 applications continue to run in 4.0 mode until I change them
  2. Are there any breaking changes in 4.5 that are likely to throw my 4.0 app offline
  3. If things go bad, can I backout of having installed 4.5?

Answer

Kyle Nunery picture Kyle Nunery · Nov 25, 2012
  1. Once 4.5 is installed then everything that used 4.0 before will use 4.5.
  2. There are a handful of compatibility issues that exist. Elegant Code describes the issue we ran into at work when upgrading to 4.5
  3. You have to uninstall 4.5 and then re install 4.0 in order to back out 4.5.