xbuild.exe.mdb: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/mono/xbuild/12.0/bin/xbuild.exe.mdb - from package: mono-dbg

You may install the required package with command apt-get install {package}

Error in other languages:
xbuild.exe.mdb: bevel nie gevind nie
xbuild.exe.mdb: comandă negăsită
xbuild.exe.mdb: comando não encontrado
xbuild.exe.mdb: commande introuvable
xbuild.exe.mdb: command not found
xbuild.exe.mdb: käsku ei ole
xbuild.exe.mdb: không tìm thấy lệnh
xbuild.exe.mdb: komanda nerasta
xbuild.exe.mdb: Kommando nicht gefunden.
xbuild.exe.mdb: kommandot finns inte
xbuild.exe.mdb: komut yok
xbuild.exe.mdb: nie znaleziono polecenia
xbuild.exe.mdb: níor aimsíodh an t-ordú
xbuild.exe.mdb: no se encontró la orden
xbuild.exe.mdb: no s'ha trobat l'ordre
xbuild.exe.mdb: opdracht niet gevonden
xbuild.exe.mdb: parancs nem található
xbuild.exe.mdb: perintah tidak ditemukan
xbuild.exe.mdb: príkaz nenájdený
xbuild.exe.mdb: příkaz nenalezen
xbuild.exe.mdb: команда не найдена
xbuild.exe.mdb: командата не е открита
xbuild.exe.mdb: 命令找不到
xbuild.exe.mdb: コマンドが見つかりません