验证用户输入是字母表中的一个字母

Question

I am trying to make a hangman game where it picks a random word from a text file of words. It then displays the word in asterisks and asks the user to guess each letter of the word if they guess right it uncovers that letter.They keep playing until they guess all the letters in the word.After the word is guessed it will display the number of misses and ask if they want to play again.

The Problem I am having is that I am trying to validate that the user entered a single character and that it is a letter of the alphabet but when the user puts in a single letter it just starts a infinite loop.not sure how to fix this.

 static void Main(string[] args)
    {
        char[] guessed = new char[26];
        char guess = ' ';
        char playAgain= ' ';
        bool validLetterInput = false;
        bool validAnswer = false;


        int amountMissed = 0, index = 0;

        do
        {
            // initilization of word and testword so that we could generate a testword with the same length as original
            char[] word = RandomLine().Trim().ToCharArray();

            char[] testword = new string('*', word.Length).ToCharArray(); 
            char[] copy = word;

            Console.WriteLine(testword);
            Console.WriteLine("I have picked a random word on animals");
            Console.WriteLine("Your task is to guess the correct word");


            while (!testword.SequenceEqual(word))
            {
                while (!validLetterInput)
                {
                    try
                    {
                        Console.Write("Please enter a letter to guess: ");
                        guess = char.Parse(Console.ReadLine().ToLower());
                        //Checks if guess is letter or not
                        if (((guess >= 'A' && guess <= 'Z') || (guess >= 'a' && guess <= 'z')))
                        {
                            validLetterInput = true;
                        }
                        else
                        {
                            Console.WriteLine("Invalid Input");
                        }


                    }
                    catch (Exception e)
                    {
                        Console.WriteLine(e.Message);

                    }
                }

                bool right = false;
                for (int j = 0; j < copy.Length; j++)
                {
                    if (copy[j] == guess)
                    {
                        Console.WriteLine("Your guess is correct.");
                        testword[j] = guess;
                        guessed[index] = guess;
                        index++;
                        right = true;
                    }
                }
                if (right != true)
                {
                    Console.WriteLine("Your guess is incorrect.");
                    amountMissed++;
                }
                else
                {
                    right = false;
                }
                Console.WriteLine(testword);

            }
            Console.WriteLine($"The word is {string.Join("",testword)}. You missed {amountMissed} times.");
            while (!validAnswer)
            {
                try
                {
                    Console.WriteLine("Do you want to guess another word? Enter y or n: ");
                    playAgain = char.Parse(Console.ReadLine());
                    if(playAgain == 'y' || playAgain == 'Y' || playAgain == 'n' || playAgain == 'N')
                    {
                        validAnswer = true;
                    }
                    else
                    {
                        Console.WriteLine("Invalid input try again");
                    }
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                }
            }
        } while (playAgain == 'y' || playAgain == 'Y');


        Console.WriteLine("Good-Bye and thanks for playing my Hangman game.");
    }
        public static string RandomLine()
    {

            // store text file in an array and return a random value
            string[] lines = File.ReadAllLines("E:\\Advanced1.csv");
            Random rand = new Random();
            return lines[rand.Next(lines.Length)].ToLower();



    }
}

Answer 1

You just have to add one line. After checking the letter and printing the testword, reset validLetterInput to false, so that it can get the next letter.

if (right != true)
{
    Console.WriteLine("Your guess is incorrect.");
    amountMissed++;
}
else
{
    right = false;
}
Console.WriteLine(testword);
validLetterInput = false;

Answer 2

It seems like you are not resetting the validLetterInput to false after first validation.

while (!testword.SequenceEqual(word))
{
    while (!validLetterInput) // <-- Need to reset this after first correct validation
    {
        try
        {
            Console.Write("Please enter a letter to guess: ");
            guess = char.Parse(Console.ReadLine().ToLower());
            //Checks if guess is letter or not
            if (((guess >= 'A' && guess <= 'Z') || (guess >= 'a' && guess <= 'z')))
            {
                validLetterInput = true;
            }
            else
            {
                Console.WriteLine("Invalid Input");
            }


        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);

        }
    }
    validLetterInput = false; // <--- ADD THIS HERE

After the first letter is accepted as valid character, it is never reset for the next letter. Once you exit the while loop where you are checking for valid input, reset the validLetterInput to false