Unity solution not compatible with visual studio

Question

Since updating to the most recent version of Unity 5.4.0f3, whenever I doubleclick on a script, it launches both Visual Studio and Monodevelop, but I get an error saying that the this version of VS (Community 2015) is unable to open my project. Monodevelop displays it's own, somewhat less clear error message. Please see the screen shots below.

I can still manually open my script using Visual Studio's file menu, but the intellisense code completion no longer works. Anyone know how to fix this? I have Visual Studio's Tools for Unity installed.

Answer 1

I was having similar issues when doing a clean download of an existing Unity project onto a fresh install of Visual Studio Community 2019.

In the end the issue for me was that, although the correct version of VS Tools for Unity was installed, it was 'Disabled' by default in VS's Manage Extensions dialog (Extensions -> Manage Extensions). Just had to click 'Enable', restart Visual Studio, and all worked as expected again.

Answer 2

Turns out it was an issue with my existing install of Visual Studio Tools for Unity (VSTU).

I found a thread where users had experienced similar problems due to an unsupported version of VSTU running on Unity5.2 and beyond. Unity 5.2+ requires VSTU 2.1 or later for VS to work correctly with Unity, more information for anyone interested is available in the documentation here.

I had VSTU 2.3 installed, but removing and reinstalling VSTU resolved the issue, so there must have been a problem with my install. If anyone else has this or a similar issue you can download the latest installer for VSTU here. Thanks to all who chimed in your responses helped me look in the right place!