Command.Registry.this C# (CSharp) Méthode

        public Command this[string cmdName]
        {
            get {
                if(_commands.ContainsKey(cmdName)) {
                    return _commands[cmdName];
                }
                else {
                    throw new KeyNotFoundException(string.Format(
                                "No command named '{0}' has been registered",
                                cmdName));
                }
            }
        }