使用 TryParse 的猜数游戏

Question

我在使用 TryParse 捕获用户在哪里输入字符串而不是 int 时无法让我的代码正常工作。如果我按照现在的样子使用它，如果输入了 int 以外的内容，我只会得到 0 的基值。我希望它向用户显示一条错误消息。

尝试过使用 TryParse 的多种不同方式，但都没有真正有用。

    static void Main(string[] args)
    {

        Random r = new Random();
        int speltal = r.Next(1,21);
        bool play = false;
        int myNum;

        while (!play)
        {
            Console.Write("\n\tGuess a number between 1 and 20: ");
            Int32.TryParse(Console.ReadLine(), out myNum);

            if (myNum < guessNum)
            {
                Console.WriteLine("\tThe number you have guessed is to low");
                Console.ReadLine();
            }

            if (myNum > guessNum)
            {
                Console.WriteLine("\tThe number you have guessed is to high");
                Console.ReadLine();
            }

            if (myNum == guessNum)
            {
                Console.WriteLine("\tCongratulations you guessed the right number!");
                Console.ReadLine();
            }

我希望它在用户输入除 int 以外的任何内容时向用户显示错误消息。根据我的老师，它还必须包含 TryParse

Answer 1

您没有捕获TryParse 的bool 输出，因此您不知道是否输入了非数字值。试试这样的：

bool isValid;
do
{
     Console.Write("\n\tGuess a number between 1 and 20: ");
     isValid = Int32.TryParse(Console.ReadLine(), out myNum);
     if(!isValid)
     {
         Console.WriteLine("\n\tInvalid input detected. Please try again.");
     }
} while(!isValid)

Answer 2

TryParse 方法只能将整数放入传递的变量中（因为它是int 类型），所以如果传递给它的值无法解析成整数，则默认值为int (0) 将分配给变量。

TryParse 告诉你它是否成功解析数字的方式是返回一个布尔指示符。

你可以试试这个：

while (true)
{
    bool valid = int.TryParse(Console.ReadLine(), out myNum);
    if(valid)
        break;
    Console.WriteLine("Input invalid. Please try again");
}

Answer 3

TryParse 返回一个布尔值，指示输入字符串是否成功解析。关于如何处理无效输入，上述两个答案都是正确的，但这里有一个更简洁的版本，它也将支持 规则，between 1 and 20:

while (true)
{    
    Console.Write("\n\tGuess a number between 1 and 20: ");

    //Checks to see if the input was successfully parsed to a integer also, performs a Trim on the input as to remove any accidental white spaces that a user might have typed in, e.g. "1000 "
    if (int.TryParse(Console.ReadLine().Trim(), out myNum))
    {
        //Checks to see if the parsed number is in the specified range
        if ((myNum > 0) && (myNum < 21))
        {
            break;
        }
        Console.WriteLine("\tThe input number was out of the specified range.");
    }
    else
    {
        Console.WriteLine("\tFailed to parse the input text.");
    }
    //Optional, makes the thread sleep so the user has the time to read the error message.
    Thread.Sleep(1500);

    //Optional, clears the console as to not create duplicates of the error message and the value of Console.Write
    Console.Clear();
}

// Continue here, if (myNum < guessNum) . . .

Answer 4

您应该使用TryParse 返回的bool。看起来像这样的东西：

更新答案：

        static void Main(string[] args)
        {
            Random random = new Random();
            int guessNum = random.Next(1, 21);

            while(true)
            {
                Console.WriteLine("Guess the number between 1 and 21.");

                if (Int32.TryParse(Console.ReadLine(), out int input))
                {
                    if (input == guessNum)
                    {
                        Console.WriteLine($"You guessed it right. The number is {input}");
                        if(ShouldContinue())
                        {
                            guessNum = random.Next();
                            continue;
                        }
                        else
                        {
                            break;
                        }
                    }

                    if (input < guessNum)
                        Console.WriteLine("The number you guessed is smaller.");
                    else
                        Console.WriteLine("The number you guessed is bigger");

                }
                else
                {
                    Console.WriteLine("Please enter a number between 1 and 21 as your guess");
                }
            }
        }

        static bool ShouldContinue()
        {
            while (true)
            {
                Console.WriteLine($"Do you want to continue playing? (y/n)");
                string continueInput = Console.ReadLine().Trim().ToLower();
                if (continueInput == "y")
                    return true;
                else if (continueInput == "n")
                    return false;
                else
                    Console.WriteLine("Invalid input!. Please choose 'y' or 'n'.");
            }
        }

旧答案：

while (true)
{
    if (Int32.TryParse(inputInt, out int myNum))
    {
       // your logic goes here, too low/high or correct answer.   
    }
}