C#实现大数字的运算

1、添加引用：System.Numerics.dll

2、添加命名空间：using System.Numerics;

3、实例：

　　3.1判断一个数字是不是质数　

       static void Main(string[] args)
        {
            Console.WriteLine("请输入一个很大的数字：");
            string bigNumber = Console.ReadLine();
            BigInteger bigInteger = BigInteger.Parse(bigNumber);
            bool isNumber=false;
            for (BigInteger i = 2; i < BigInteger.Pow(bigInteger, 2);i++ )
            {
                if (bigInteger % i == 0)
                {
                    isNumber = true;
                    break;
                }
            }
            if (isNumber)
            {
                Console.WriteLine("不是质数");
            }
            else
            {
                Console.WriteLine("是质数");
            }
            Console.ReadLine();
        }

　　3.2实现两个大数的加减乘除

     

        static void Main(string[] args)
        {
            Console.Write("请输入第一个大数字:");
            string bigNum1 = Console.ReadLine();
            BigInteger bigInt1 = BigInteger.Parse(bigNum1);

            Console.Write("请输入第二个大数字:");
            string bigNum2 = Console.ReadLine();
            BigInteger bigInt2 = BigInteger.Parse(bigNum2);
            Console.Write(Environment.NewLine);

            BigInteger addNum = bigInt1 + bigInt2;
            BigInteger subNum = bigInt1 - bigInt2;
            BigInteger purNum = bigInt1 * bigInt2;
            BigInteger divNum = bigInt1 / bigInt2;

            Console.WriteLine("两大数相加结果为：{0}",addNum);
            Console.WriteLine("两大数相减结果为：{0}",subNum);
            Console.WriteLine("两大数相乘结果为：{0}",purNum);
            Console.WriteLine("两大数相除结果为：{0}",divNum);

            Console.ReadLine();
        }

4、这里我没有去深入如何实现大数字的运算，猜测可以用字符数组来完成  参考文章：http://www.codeproject.com/Articles/60108/BigInteger-Library