private void HandleOperatorInput(char key)
{
if (operation != null && isResultUpdated)
{
result = operation.Operate(result, Convert.ToDouble(operand.ToString()));
}
else
{
result = Convert.ToDouble(operand.ToString());
}
operation = operatorFactory.GetOperation(key);
operand.Clear().Append(result.ToString());
isOperandConsumed = true;
isResultUpdated = true;
}