c# - 如何修复 "The type or namespace name could not be found"？

Question

这是我之前问题的后续问题 https://codereview.stackexchange.com/questions/12165/efficency-in-c/12169 ，我尽力使用 BigIntegers 代替 ulongs，但我一定做错了什么。我是 C# 的新手，我熟悉 Java。这是我最好的转化机会:

using System;

namespace System.Numerics{

      public class Factorial{

             public static void Main(){

             String InString = Console.ReadLine();

             BigInteger num = 0;

             BigInteger factorial = 1;

             try {
                 num = BigInteger.Parse(InString);
                 Console.WriteLine(num);
                 }
             catch (FormatException) {

                  Console.WriteLine("Unable to convert the String into a BigInteger");
            }



            for (BigInteger forBlockvar = num; forBlockvar > 1; forBlockvar--){

                     factorial *= forBlockvar;

            }

            Console.WriteLine("The Factorial for the Given input is:");

            Console.WriteLine(factorial);
    }
}
}

我得到了以下错误:

prog.cs(11,18): error CS0246: The type or namespace name `BigInteger' could not be found. Are you missing a using directive or an assembly reference?
prog.cs(13,18): error CS0246: The type or namespace name `BigInteger' could not be found. Are you missing a using directive or an assembly reference?
prog.cs(26,22): error CS0246: The type or namespace name `BigInteger' could not be found. Are you missing a using directive or an assembly reference?

这个错误是什么意思，我该如何解决？

Answer 1

您需要添加对 System.Numerics.dll 的引用(在解决方案资源管理器中右键单击“引用”并选择“添加引用”)。

此外，放入 using System.Numerics 而不是让您的方法的 namespace 成为那样(即，将其命名为对您的代码库更具描述性的名称)。