如何修复"无法找到类型或命名空间名称"？

Question

这是我之前的问题https://codereview.stackexchange.com/questions/12165/efficency-in-c/12169的后续内容,我尽力使用BigIntegers代替ulongs,但我必须做点什么错误.我是C#的新手,我熟悉Java.这是我转换时的最佳镜头:

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);
    }
}
}

我收到以下错误:

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?

这个错误意味着什么,我该如何解决？

Answer 1

您需要在System.Numerics.dll中添加引用(右键单击"解决方案资源管理器"中的"引用"并选择"添加引用").

另外,放入using System.Numerics而不是让你的方法的命名空间(即将它命名为代码库更具描述性).