1 BigInteger num1 = BigInteger.Parse("乘数一");2 BigInteger num2 = BigInteger.Parse("乘数二");3 Console.WriteLine(num1* num2);4 Console.ReadKey();

 1             static string getbackresult(string s1, string s2) 2             { 3                 string lastResult = ""; 4                 int ten1 = -1; 5                 int[] result = new int[s1.Length + s2.Length];//用以记录计算结果 6                 for (int i = s1.Length - 1; i >=0; i--) 7                 { 8                     int c1 = Convert.ToInt16(s1[i].ToString());//从s1中从后往a前取一个数并记录这个数的位置 9                     ten1++;10                     int resultindex = result.Length - 1 - ten1;11                     for (int j = s2.Length - 1; j >=0; j--)12                     {13                         int c2 = Convert.ToInt16(s2[j].ToString());//从?s2中从后往前取一个数14                         int cc = c1 * c2 + result[resultindex];15                         if (cc > 10)16                         {17                             result[resultindex] = cc % 10;18                             int lastindex = resultindex - 1;  //往前移动一位19                             int lastvalue = result[lastindex] + cc / 10;  //把刚刚得到的十位的数字赋值到前面20                             while (cc > 10)21                             {22                                 cc = result[lastindex] + cc / 10;23                                 result[lastindex] = cc % 10;24                                 lastindex--;//进位25                             }26                         }27                         else28                         {29                             result[resultindex] = cc;30                         }31                         resultindex--;//进位32                     }33                 }34                 StringBuilder sb = new StringBuilder();35                 foreach (int item in result)36                 {37                     sb.Append(item);38                 }39                 lastResult = sb.ToString();40                 if (lastResult[0]=='0')41                 {42                     lastResult = lastResult.Substring(1);43                 }44                 return lastResult;45             }