Uninstalling Mono on Mac OS X

remove-mono.sh

#!/bin/sh -x

#This script removes Mono from an OS X System.  It must be run as root

rm -r /Library/Frameworks/Mono.framework

rm -r /Library/Receipts/MonoFramework-*

for dir in /usr/bin /usr/share/man/man1 /usr/share/man/man3 /usr/share/man/man5; do
   (cd ${dir};
    for i in `ls -al | grep /Library/Frameworks/Mono.framework/ | awk '{print $9}'`; do
      rm ${i}
    done);
done

Modern instructions are simpler it seems:

sudo rm -rf /Library/Frameworks/Mono.framework
sudo pkgutil --forget com.xamarin.mono-MDK.pkg
sudo rm /etc/paths.d/mono-commands

@king-of-poppk thank you sir, just save my day !