c# 堆栈四则运算

public static Double GetResultFromStr(string source)
       {
           string str = InsertBlank(source);
           string rpnExperssion = ConvertToRPN(str);
           return GetResult(rpnExperssion);

       }
  
        private static double GetValue(double left, double right, char _operator)  
        {  
            switch (_operator)  
            {  
                case '+':  
                    return left+right;  
                case '-':  
                    return left-right;  
               case '*':  
                    return left*right;  
                case '/':  
                    return left/right;  
            }  
            return 0;  
        }

        private static double GetResult(string source)  
        {
            try
            {
                source = source.Trim();
                Stack<string> stack = new Stack<string>();
                var list = source.Split(' ');
                for (int i = 0; i < list.Length; i++)
                {
                    string current = list[i];
                    //bool  b = Regex.IsMatch(strNum, "^[0-9]*{1}quot;);  
                    if (GetNum(current))
                    {
                        stack.Push(current);
                    }
                    else if (OperatorLevel.ContainsKey(current))
                    {
                        double right = double.Parse(stack.Pop());
                        double left = double.Parse(stack.Pop());
                        stack.Push(GetValue(left, right, current[0]).ToString());
                    }
                }
                string aaa = stack.Pop().ToString();
                return double.Parse(aaa);
            }
            catch (Exception e)
            { }
            return 0;
        }

        private static string ConvertToRPN(string source)  
        {
            try
            {
                StringBuilder result = new StringBuilder();
                Stack<string> stack = new Stack<string>();
                string[] list = source.Split(' ');
                for (int i = 0; i < list.Length; i++)
                {
                    string current = list[i];
                    //if (Regex.IsMatch(current, "^([0-9]{1,}){1}quot;"))
                    if (GetNum(current))
                    {
                        result.Append(current + " ");
                    }
                    else if (OperatorLevel.ContainsKey(current))
                    {
                        if (stack.Count > 0)
                        {
                            var prev = stack.Peek();
                            if (prev == "(")
                            {
                                stack.Push(current);
                                continue;
                            }
                            if (current == "(")
                            {
                                stack.Push(current);
                                continue;
                            }
                            if (current == ")")
                            {
                                while (stack.Count > 0 && stack.Peek() != "(")
                                {
                                    result.Append(stack.Pop() + " ");
                                }
                                //Pop the "("  
                                stack.Pop();
                                continue;
                            }
                            if (OperatorLevel[current] < OperatorLevel[prev])
                            {
                                while (stack.Count > 0)
                                {
                                    var top = stack.Pop();
                                    if (top != "(" &&
                                        top != ")")
                                    {
                                        result.Append(top + " ");
                                    }
                                    else
                                    {
                                        break;
                                    }
                                }
                                stack.Push(current);
                            }
                            else
                            {
                                stack.Push(current);
                            }
                        }
                        else
                        {
                            stack.Push(current);
                        }
                    }
                }
                if (stack.Count > 0)
                {
                    while (stack.Count > 0)
                    {
                        var top = stack.Pop();
                        if (top != "(" && top != ")")
                        {
                            result.Append(top + " ");
                        }
                    }
                }
                return result.ToString().Trim();
            }
            catch(Exception e)
            { }
            return "";
        }

        private static string InsertBlank(string source)  
       {  
            StringBuilder sb = new StringBuilder();  
            var list = source.ToCharArray();  
            foreach (var temp in list)  
            {  
                if (OperatorLevel.ContainsKey(temp.ToString()))  
                {  
                    sb.Append(" ");  
                    sb.Append(temp.ToString());  
                    sb.Append(" ");  
               }  
                else  
                {  
                    sb.Append(temp);  
                }  
            }  
            return sb.ToString();          }

        private static Dictionary<string, int> OperatorLevel  
       {  
           get  
            {  
                if(_operatorLevel==null)  
                {  
                    _operatorLevel = new Dictionary<string, int>();  
                    _operatorLevel.Add("+", 0);  
                    _operatorLevel.Add("-", 0);  
                    _operatorLevel.Add("(", 1);  
                    _operatorLevel.Add("*", 1);  
                    _operatorLevel.Add("/", 1);  
                    _operatorLevel.Add(")", 0);  
                }  
                return _operatorLevel;  
            }  
        }  

           /// <summary>  
       /// 验证是不是数字（包含整数和小数）  
       /// </summary>  
       /// <param name="str"></param>  
       /// <returns></returns>  
       private static bool GetNum(string str)  
       {
           bool b = false;
           try
           {
               double.Parse(str);
               b = true;
           }
           catch (Exception e)
           { 

           }
           return b;
      }