C# 计算加减乘除

static void Main(string[] args)
{
/*
* 命题：计算 加 减 乘 除，不含括号
*/
var str = "8*8*8-100*2";
//计算乘法
str = Calc(str, '*');
str = Calc(str, '/');
str = Calc(str, '+');
str = Calc(str, '-');
Console.WriteLine(str);
Console.Read();
}
private static string Calc(string exp,char sign)
{
var r = new Regex(string.Format(@"(\d+)\{0}(\d+)", sign));
var exps = r.Matches(exp);
if (exps.Count == 0) return exp;
exp = exps.Cast<Match>().Aggregate(exp, (current, p) => current.Replace(p.ToString(), Operate(p.ToString(), sign).ToString()));
exp = Calc(exp, sign);
return exp;
}
private static double Operate(string exp,char sign)
{
var arr = exp.Split(sign);
double result = 0;
var numA = NumberHelper.FormatDouble(arr[0]);
var numB = NumberHelper.FormatDouble(arr[1]);
switch (sign)
{
case '+':
result = numA + numB;
break;
case '-':
result = numA - numB;
break;
case '*':
result = numA * numB;
break;
case '/':
result = numB != 0 ? numA/numB : 0;
break;
}
return result;
}