Console.WriteLine("Please enter a number:"); int number = int.Parse(Console.ReadLine()); while (number <= 0) { Console.WriteLine("Sorry,please enter a positive value."); number = Int32.Parse(Console.ReadLine()); } Console.WriteLine("Please enter " + number + " words:"); string[] words = new string[number]; for (int n = 0; n < number; n++) { Console.WriteLine($"Please enter word {n + 1}"); string word = Console.ReadLine(); while (word.Length < 1) { Console.WriteLine("Sorry,your word must have at least one character"); word = Console.ReadLine(); } words[n] = word; } Console.WriteLine("You enter these words:"); foreach (string s in words) { Console.WriteLine(s); }; Console.WriteLine("Please enter a character:"); char letter = char.Parse(Console.ReadLine()); if (char.IsLetter(letter)) { string joinedWords = string.Join("", words).ToLower(); int count = 0; for (int i = 0; i < joinedWords.Length; i++) { if (joinedWords[i] == letter) { count++; } } if (count == 0) { Console.WriteLine("The letter you entered does not appear"); } else { double per = Convert.ToDouble(count) / Convert.ToDouble(joinedWords.Length); if (per > 0.25) { Console.WriteLine("The letter " + letter + " appears " + count + " times in the array. This letter makes up more than 25 % of the total number of characters."); } else { Console.WriteLine("The letter " + letter + " appears " + count + " times in the array. This letter makes up less than 25 % of the total number of characters."); } } } else { Console.WriteLine("Incorrect letter format entered,Please enter again:"); letter = char.Parse(Console.ReadLine()); } 改进代码

以下是改进后的代码，主要是加入了异常处理和代码重构：

using System;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            int number = ReadPositiveInt("Please enter a number:");
            string[] words = new string[number];

            for (int n = 0; n < number; n++)
            {
                words[n] = ReadNonEmptyString($"Please enter word {n + 1}:");
            }

            Console.WriteLine("You entered these words:");
            foreach (string word in words)
            {
                Console.WriteLine(word);
            }

            char letter = ReadLetter("Please enter a character:");

            string joinedWords = string.Join("", words).ToLower();
            int count = CountLetter(letter, joinedWords);

            if (count == 0)
            {
                Console.WriteLine($"The letter {letter} does not appear");
            }
            else
            {
                double per = Convert.ToDouble(count) / Convert.ToDouble(joinedWords.Length);
                if (per > 0.25)
                {
                    Console.WriteLine($"The letter {letter} appears {count} times in the array. This letter makes up more than 25% of the total number of characters.");
                }
                else
                {
                    Console.WriteLine($"The letter {letter} appears {count} times in the array. This letter makes up less than 25% of the total number of characters.");
                }
            }
        }

        static int ReadPositiveInt(string message)
        {
            int number;
            while (true)
            {
                try
                {
                    Console.WriteLine(message);
                    number = int.Parse(Console.ReadLine());
                    if (number > 0)
                    {
                        return number;
                    }
                    else
                    {
                        Console.WriteLine("Sorry, please enter a positive value.");
                    }
                }
                catch (FormatException)
                {
                    Console.WriteLine("Invalid input format, please enter an integer.");
                }
            }
        }

        static string ReadNonEmptyString(string message)
        {
            string word;
            while (true)
            {
                Console.WriteLine(message);
                word = Console.ReadLine();
                if (!string.IsNullOrEmpty(word))
                {
                    return word;
                }
                else
                {
                    Console.WriteLine("Sorry, your word must have at least one character.");
                }
            }
        }

        static char ReadLetter(string message)
        {
            char letter;
            while (true)
            {
                try
                {
                    Console.WriteLine(message);
                    letter = char.Parse(Console.ReadLine());
                    if (char.IsLetter(letter))
                    {
                        return letter;
                    }
                    else
                    {
                        Console.WriteLine("Incorrect letter format entered, please enter again:");
                    }
                }
                catch (FormatException)
                {
                    Console.WriteLine("Invalid input format, please enter a letter.");
                }
            }
        }

        static int CountLetter(char letter, string word)
        {
            int count = 0;
            foreach (char c in word)
            {
                if (c == letter)
                {
                    count++;
                }
            }
            return count;
        }
    }
}

改进后的代码加入了异常处理，可以更好地处理输入错误的情况。同时，代码也进行了重构，使得逻辑更加清晰，可读性更高。