public void ExecuteInstructions(string instructions)
{
instructions = instructions.ToLower();
foreach (char i in instructions)
{
switch (i)
{
case 'l':
_robot.CommandLeft();
break;
case 'r':
_robot.CommandRight();
break;
case 'm':
_robot.CommandMove();
break;
default: throw new ArgumentException("Invalid instruction " + i);
}
}
}