如何在使用 Substring 和 length 方法时避免 System.ArgumentOutOfRangeException

Question

我正在创建一个猜谜游戏，但每次我第二次输入正确的字符时它都会抛出异常，但起初看起来很好，但当我再次猜到正确的字母时，我得到异常，异常是 System.ArgumentOutOfRangeException : 'startIndex 不能大于字符串的长度。 （参数'startIndex'）我尝试了所有可能的方法来解决这个问题，但我仍然找不到正确的解决方案希望你能帮助我。

using System;
using System.Collections;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            String secret = " ", temp = " ", lalagyan = " ", answer="";
            int count = 0, num = 5;
            bool bol = false;
            var random = new Random();
            ArrayList list = new ArrayList { "one", "two", "three", "four" };
            int index = random.Next(list.Count);
            String word = list[index].ToString();

            for (int i = 0; i < word.Length; i++)
            {
                secret = word.Replace(word, "-");
                Console.Write(secret);
            }
            do
            {
                count++;
                Console.WriteLine("\nEnter a letter ");
                Console.WriteLine("Remaining Chances: " + num);
                Console.WriteLine("Clue: the word is " + word.Length + " letters");
                Console.Write("Answer: ");
                answer = Console.ReadLine();
                num--;
                Console.WriteLine("");
                for (int i = 0; i < word.Length; i++)
                {
                    //dito
                    if (answer.Equals(Convert.ToString(word[i])))
                    {
                        if (!bol)
                        {
                            temp += Convert.ToString(word[i]);
                        }
                        else
                        {
                            //error around here
                            Console.Write("Correct Letter\n");
                            lalagyan = Convert.ToString(word[i]).Replace("-", answer);
                            temp = temp.Substring(0, i) + lalagyan + temp.Substring(i + 1, temp.Length - i + 1);
                        }
                    }
                    else
                    {
                        if (!bol)
                        {
                            temp += "-";
                        }
                    }
                }
                bol = true;
                Console.Write(temp);
            }
            while (count < 5);
            Console.Write("\nEnter Your Final Guess: ");
            answer = Console.ReadLine();
            answer = answer.ToUpper();
            if (answer.Equals(index))
            {
                Console.WriteLine("\nYour Guess Is Correct!");
            }
            else
            {
                Console.WriteLine("\nYour Guess Is Wrong!");
            }
        }
    }
}

输出：

---
Enter a letter
Remaining Chances: 5
Clue: the word is 3 letters
Answer: o

 --o
Enter a letter
Remaining Chances: 4
Clue: the word is 3 letters
Answer: t

Correct Letter
t --o
Enter a letter
Remaining Chances: 3
Clue: the word is 3 letters
Answer: w

Correct Letter
tw--o
Enter a letter
Remaining Chances: 2
Clue: the word is 3 letters
Answer: o

Correct Letter
two-o
Enter a letter
Remaining Chances: 1
Clue: the word is 3 letters
Answer: o

Correct Letter
two-o
Enter Your Final Guess: two

Your Guess Is Wrong!

Answer 1

ArgumentOutOfRange 异常通常意味着您正在尝试获取超出数组/集合边界的值。

在您的情况下，如果用户猜测最后一个字母，则 i 值如下：

temp = temp.Substring(0, i) + lalagyan + temp.Substring(i + 1, temp.Length);

第一个temp.Substring(0,i) 将返回整个临时字符串，第二个temp.Substring(i+1, temp.Length) 将尝试从最后一个索引开始返回一个长度为temp.Length 的字符串 - 因为这是不可能的，它可能会导致异常。

查看这行代码应该做什么。

Answer 2

Substring 中的第二个参数是子字符串的长度，这就是为什么

  temp.Substring(i + 1, temp.Length)

是错误的：temp.Length 是 整个 字符串的长度，这就是它对于子字符串而言 太大 的原因。你可以把它写成

  temp = temp.Substring(0, i) + lalagyan + temp.Substring(i + 1);

这里temp.Substring(i + 1) 的意思是“从i + 1 开始，直到结束”。

编辑：如果是任意i，您也应该检查i：

  temp = 
      i <= 0 ? lalagyan + temp 
    : i >= temp.Length ? temp + lalagyan
    : temp.Substring(0, i) + lalagyan + temp.Substring(i + 1);