案例切换阵列中发生的'System.IndexOutOfRangeException'

Question

在一两年前我第一次做这个时没有的地方向我抛出"System.IndexOutOfRangeException"。我问了我现在的教授，但他只是说"行得通，没有问题"。我们都得到了例外，所以我想知道为什么老师没有。这是代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
/* Author: Austin Bigge
* This program will ask for a ten digit alphanumeric
* number and return the numeric number.
*/
namespace alphanumeric
{
class Program
{
    static void Main(string[] args)
    {
        // Switch for alphanumeric entry
        string numberString; //alphanumberic entry
        char currentLetter;
        string invalue;
        double pnumber; //returned single numeric phone number
        int i; //i = the current character space
        //User prompt
        Console.WriteLine("This program will ask for an alphanumberic phone ");
        Console.WriteLine("number and change it into a numeric phone number.");
        Console.WriteLine("! Alphanumeric characters only !");
        Console.WriteLine("! No Spaces, Dashes, or Symbols !");
        Console.Write("What is the 10 digit phone number? ");
        invalue = Console.ReadLine();
        numberString = invalue;
        char[] array = numberString.ToCharArray();
        for (i = 0; i < array.Length; i++) //for loop
        // gets the current letter at position "i"
        currentLetter = array[i];
        switch (i) //case switch for possible entries
        {
            case '1':
                pnumber = 1; Console.WriteLine(pnumber); break;
            case '2':
            case 'a':
            case 'A':
            case 'b':
            case 'B':
            case 'c':
            case 'C':
                pnumber = 2; Console.WriteLine(pnumber); break;
            case '3':
            case 'd':
            case 'D':
            case 'e':
            case 'E':
            case 'f':
            case 'F':
                pnumber = 3; Console.WriteLine(pnumber); break;
            case '4':
            case 'g':
            case 'G':
            case 'h':
            case 'H':
            case 'i':
            case 'I':
                pnumber = 4; Console.WriteLine(pnumber); break;
            case '5':
            case 'j':
            case 'J':
            case 'k':
            case 'K':
            case 'l':
            case 'L':
                pnumber = 5; Console.WriteLine(pnumber); break;
            case '6':
            case 'm':
            case 'M':
            case 'n':
            case 'N':
            case 'o':
            case 'O':
                pnumber = 6; Console.WriteLine(pnumber); break;
            case '7':
            case 'p':
            case 'P':
            case 'q':
            case 'Q':
            case 'r':
            case 'R':
            case 's':
            case 'S':
                pnumber = 7; Console.WriteLine(pnumber); break;
            case '8':
            case 't':
            case 'T':
            case 'u':
            case 'U':
            case 'v':
            case 'V':
                pnumber = 8; Console.WriteLine(pnumber); break;
            case '9':
            case 'w':
            case 'W':
            case 'x':
            case 'X':
            case 'y':
            case 'Y':
            case 'z':
            case 'Z':
                pnumber = 9; Console.WriteLine(pnumber); break;
            case '0':
                pnumber = 0; Console.WriteLine(pnumber); break;
            case ' ': Console.WriteLine("Bad Value, do not use spaces"); break;
            default: Console.WriteLine("Bad Value, use only numbers or letters."); break;

        }
    }
}

}

任何帮助都是感激的，他一直向我寻求帮助，我一直告诉他，他和我一样了解。p.s.调试器针对这个异常指向第36行

编辑：

是的，你是对的，现在我在第37行"currentLetter"有一个未分配的变量，我想我已经初始化了它，当我试图在错误处初始化它时，它告诉我它已经初始化了。。。我一定删除了我的工作程序。我发现这个文件有几个空的迭代。我真的很感激你的帮助，我的朋友肯定也会。

我想我已经解决了，我用"i"替换了"currentLetter"

现在阵列不工作了。仅返回默认情况。再次卡住。我编辑了我的进度。

编辑

当我们集思广益时发现了一堆错误。完成的程序如下。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
    class Program
    {
    static void Main(string[] args)
    {
        // Switch for alphanumeric entry
        string numberString; //alphanumberic entry
        char currentLetter;
        string invalue;
        double pnumber; //returned single numeric phone number
        int i; //i = the current character space
        //User prompt
        Console.WriteLine("This program will ask for an alphanumberic phone ");
        Console.WriteLine("number and change it into a numeric phone number.");
        Console.WriteLine("! Alphanumeric characters only !");
        Console.WriteLine("! No Spaces, Dashes, or Symbols !");
        Console.Write("What is the 10 digit phone number? ");
        invalue = Console.ReadLine();
        numberString = invalue;
        char[] array = numberString.ToCharArray();
        for (i = 0; i < 10; i++)
        {
            //for loop
            //numberString = invalue.ToString().ToCharArray()[i]);
            // gets the current letter at position "i"
            currentLetter = array[i];
            switch (currentLetter) //case switch for possible entries
            {
                case '0':
                    pnumber = 0; Console.Write(pnumber); break;
                case '1':
                    pnumber = 1; Console.Write(pnumber); break;
                case '2':
                case 'a':
                case 'A':
                case 'b':
                case 'B':
                case 'c':
                case 'C':
                    pnumber = 2; Console.Write(pnumber); break;
                case '3':
                case 'd':
                case 'D':
                case 'e':
                case 'E':
                case 'f':
                case 'F':
                    pnumber = 3; Console.Write(pnumber); break;
                case '4':
                case 'g':
                case 'G':
                case 'h':
                case 'H':
                case 'i':
                case 'I':
                    pnumber = 4; Console.Write(pnumber); break;
                case '5':
                case 'j':
                case 'J':
                case 'k':
                case 'K':
                case 'l':
                case 'L':
                    pnumber = 5; Console.Write(pnumber); break;
                case '6':
                case 'm':
                case 'M':
                case 'n':
                case 'N':
                case 'o':
                case 'O':
                    pnumber = 6; Console.Write(pnumber); break;
                case '7':
                case 'p':
                case 'P':
                case 'q':
                case 'Q':
                case 'r':
                case 'R':
                case 's':
                case 'S':
                    pnumber = 7; Console.Write(pnumber); break;
                case '8':
                case 't':
                case 'T':
                case 'u':
                case 'U':
                case 'v':
                case 'V':
                    pnumber = 8; Console.Write(pnumber); break;
                case '9':
                case 'w':
                case 'W':
                case 'x':
                case 'X':
                case 'y':
                case 'Y':
                case 'z':
                case 'Z':
                    pnumber = 9; Console.Write(pnumber); break;
                case ' ':
                    Console.WriteLine();
                    Console.WriteLine("Bad Value, do not use spaces");
                    Console.Write("What is the 10 digit phone number? ");
                    invalue = Console.ReadLine();
                    numberString = invalue;
                    array = numberString.ToCharArray();
                    i = 0;
                    break;
                default:
                    Console.WriteLine();
                    Console.WriteLine("Bad Value, use only numbers or letters.");
                    Console.Write("What is the 10 digit phone number? ");
                    invalue = Console.ReadLine();
                    numberString = invalue;
                    array = numberString.ToCharArray();
                    i = 0;
                    break;
            }
        }
        Console.WriteLine();
        Console.WriteLine("Press any key to close this window");
        Console.ReadLine();
    }
}
}

谢谢你让我们开始修复，我们都很感激，朋友！

Answer 1

for行上的分号是导致问题的原因：

for (i = 0; i < array.Length; i++) ; //for loop

for循环后面应该跟着一个块，但在这种情况下，由于它后面跟着一个分号，所以后面的代码不是循环的一部分，而只是执行一次的常规代码。

因此，for循环使用一个空体执行，当它完成时，i有一个数组长度的值，当然比引发异常的最大索引高一个。

要解决此问题，请在循环中要包含的代码组周围创建一个块（花括号）。

这也带来了一个单独的问题——for循环通常会在循环本身中声明索引器——如果您在for中定义了i，那么它将超出以下行的范围，并且更容易看到您的错误，因为这将是一个编译器错误。

for (int i = 0; i < array.Length; i++)
{
    // Your code here
}
// i is no longer in scope