csharp2: 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 CentOS possible default full paths are:

/usr/bin/csharp2 - from package: mono-core

You may install the required package with command yum install {package}

Error in other languages:
csharp2: bevel nie gevind nie
csharp2: comandă negăsită
csharp2: comando não encontrado
csharp2: commande introuvable
csharp2: command not found
csharp2: käsku ei ole
csharp2: không tìm thấy lệnh
csharp2: komanda nerasta
csharp2: Kommando nicht gefunden.
csharp2: kommandot finns inte
csharp2: komut yok
csharp2: nie znaleziono polecenia
csharp2: níor aimsíodh an t-ordú
csharp2: no se encontró la orden
csharp2: no s'ha trobat l'ordre
csharp2: opdracht niet gevonden
csharp2: parancs nem található
csharp2: perintah tidak ditemukan
csharp2: príkaz nenájdený
csharp2: příkaz nenalezen
csharp2: команда не найдена
csharp2: командата не е открита
csharp2: 命令找不到
csharp2: コマンドが見つかりません