使用字符串解析的方式完成计算器的设计思路

//声明：目前所有操作符都是单字符型        //根据合理的字符串，返回值        PRivate decimal getValue(string str)        {            decimal result = 0;//存储要返回的结果            int OperatorIndex = -1;//存储当前操作符在字符串中的索引            string operatorType = "";//存储当前操作符的类型            operatorIndex = getOperatorIndex(str);            operatorType = getOperatorType(operatorIndex, str);            int operator0Index = -1;//存储当前操作符前一个操作符0在字符串中的索引            //string operator0Type = "";//存储当前操作符的前一个操作符0的类型            operator0Index = getOperator0Index(str, operatorIndex);            //operator0Type = getOperatorType(operator0Index, str);            int operator1Index = -1;//存储当前操作符后一个操作符1在字符串中的索引            //string operator1Type = "";//存储当前操作符的后一个操作符1的类型            operator1Index = getOperator1Index(str, operatorIndex);            //operator1Type = getOperatorType(operator1Index, str);            double num1 = 0.1000000000000000000001;//存储第一个操作数的值            double num2 = 0.2000000000000000000002;//存储第二个操作数的值            num1 = getNum1(operatorIndex, operator0Index, str);            num2 = getNum2(operatorIndex, operator1Index, str);            result = Convert.ToDecimal(getResult(num1, num2, operatorType));            return result;        }        //目前字符串以数字开头，找到优先操作符，并返回在字符串中的索引        private int getOperatorIndex(string str)        {            int operatorIndex = -1;//存储第一个操作符所在的索引            for (int i = 0; i < str.Length; i++)            {                switch (str[i])                {                    case '*':                        {                            operatorIndex = i;                        } break;                    case '/':                        {                            operatorIndex = i;                        } break;                    case '+':                        {                            operatorIndex = i;                        } break;                    case '-':                        {                            operatorIndex = i;                        } break;                }            }            return operatorIndex;        }        //根据优先操作符索引，操作符所在字符串，返回前一个操作符的索引，有则返回索引，无则返回0        private int getOperator0Index(string str, int operatorIndex)        {            int operator0Index = -1;//存储前一个操作符所在的索引            for (int i = operatorIndex - 1; i >= 0; i--)            {                switch (str[i])                {                    case '*':                        {                            operator0Index = i;                        } break;                    case '/':                        {                            operator0Index = i;                        } break;                    case '+':                        {                            operator0Index = i;                        } break;                    case '-':                        {                            operator0Index = i;                        } break;                }            }            if (operator0Index == -1)            {                operator0Index = 0;            }            return operator0Index;        }        //根据优先操作符索引，操作符所在字符串，返回后一个操作符的索引，有则返回索引，无则返回字符串最后有一位的索引        private int getOperator1Index(string str, int operatorIndex)        {            int operator1Index = -1;//存储后一个操作符所在的索引            for (int i = operatorIndex + 1; i < str.Length - 1; i++)            {                switch (str[i])                {                    case '*':                        {                            operator1Index = i;                        } break;                    case '/':                        {                            operator1Index = i;                        } break;                    case '+':                        {                            operator1Index = i;                        } break;                    case '-':                        {                            operator1Index = i;                        } break;                }            }            if (operator1Index == -1)            {                operator1Index = str.Length - 1;            }            return operator1Index;        }        //根据操作符的索引，返回操作符的类型        private string getOperatorType(int operatorIndex, string str)        {            string operatorType = "";            if (operatorIndex != 0 || operatorIndex != str.Length)            {                operatorType = str[operatorIndex].ToString();            }            return operatorType;        }        //根据当前操作符的索引，前一个操作符的索引，操作符所在字符串，返回当前操作符前一个操作数        private double getNum1(int OperatorIndex, int Operator0Index, string str)        {            double num1 = 0.10000000000000000000001;            num1 = Convert.ToDouble(str.Substring(Operator0Index, OperatorIndex - Operator0Index));            return num1;        }        //根据当前操作符的索引，后一个操作符的索引，操作符所在字符串，返回当前操作符后一个操作数        private double getNum2(int OperatorIndex, int Operator1Index, string str)        {            double num2 = 0.200000000000000000000002;            num2 = Convert.ToDouble(str.Substring(OperatorIndex + 1, Operator1Index - OperatorIndex));            return num2;        }        //根据两个操作数和一个操作符，返回结果        private double getResult(double num1, double num2, string operatorType)        {            double result = 0.000000000000000000000000001;            switch (operatorType)            {                case "+":                    {                        result = num1 + num2;                    } break;                case "-":                    {                        result = num1 - num2;                    } break;                case "*":                    {                        result = num1 * num2;                    } break;                case "/":                    {                        result = num1 / num2;                    } break;            }            return result;        }        private void btn_Empty_Click(object sender, EventArgs e)        {            textBox1.Text = "";        }        private void btn_Back_Click(object sender, EventArgs e)        {            textBox1.Text = textBox1.Text.Substring(0, textBox1.Text.Length - 1);        }