For Debian 8, there is no old package of Mono before 5.0. You have to install Mono manualy (./configure, make, make install).
You can download the package from the repository directly : https://fossies.org/linux/misc/mono-sources/mono/mono-22.214.171.124.tar.bz2/
Before the next step bellow, uninstall the Mono 5.0 with the apt-get remove and apt-get purge commands.
- Upload the archived file in /src/
- Use tar command to un-archive the archive uploaded (tar -xvf mono-126.96.36.199.tar.bz2)
- Install cmake via (apt-get install cmake)
- Go to the un-archived folder /src/mono4.8/ with cd command.
- make install
Then don’t forget to apt-get update and apt-get upgrade.
Start your server and it works