“Cannot start Omnisharp because Mono version >=3.10.0 is required”

Question

I just installed Visual Studio Code and when I started it, it gives me this error. When I try to execute my example application, it gives me TypeLoadExceptions.

Answer 1

When you installed it, you probably used

sudo apt-get install mono-complete

In my case, this installed Mono 3.2.8 which is evidently lower than 3.10.0. I couldn't manage to upgrade my Mono installation to a more recent version until I found this workaround:

sudo apt-get install mono-devel

This will install the developer package which, as of yesterday, comes with Mono 4.0.1. This will replace your existing Mono 3.2.8 installation with the newest version and when you restart VS Code, you'll notice that the error is gone and everything seems to work perfectly. Likewise, executing a program will also no longer have TypeLoadExceptions.

I blogged about this in more detail here.