Question

我对编程和编码很陌生，而我最近刚刚开始参加一周前的计算机科学工程课程。出于某种原因，我继续在int32.parse行中获得系统格式异常。我不明白我做错了什么。如果可以的话请帮忙。我的任务是：

创建一个简单的应用程序，其中包含适当类型的变量存储用户名和三个测试成绩。
向用户索取此信息并妥善保存。
创建一个变量来存储用户的测试平均值。
计算并分配此值使用用户提供给您的存储信息。

我的代码如下：

class MainClass
{
    public static void Main (string[] args)
    {
        Console.WriteLine ("Please enter your name: ");
        string name; 
        name = Console.ReadLine ();
        Console.WriteLine ("Hello, " + name); 
        int score;
        Console.Write ("What are your last three test scores: "); 
        score = Int32.Parse(Console.ReadLine ());
        Console.WriteLine("Your test scores are" + score + "90,92,95");}
}

Answer 1

Console.Readline()返回一个字符串。在您的情况下，此字符串可能类似于"96,92,99"。

string inputs = Console.ReadLine();

第一步是使用逗号作为分隔符将字符串拆分为三个字符串，如"96"，"92"，"99"

string[] parts = input.Split(',');

现在每个字符串需要逐个转换为整数

// Create array of integers with the same size as the array of parts
int[] grades = new int[parts.Length];
// Loop through the input parts and convert them into integers
for(i=0; i<parts.Length; i++)
{
    // Use `TryParse()` as it wont throw an Exception if the inputs are invalid
    int.TryParse(parts[i], out grades[i]);
}

现在你可以做一些事情来计算平均值。我更喜欢使用内置函数，例如.Average()或.Sum()

Console.WriteLine("The average grade is " + grades.Average().ToString("F1"));

您可以使用string.Join()函数将值数组合并到逗号分隔的字符串中。

Console.WriteLine("I parsed these values: " + string.Join(",", grades));

因此，例如，如果输入无效，您将看到0代替无效值。这是一个示例控制台输出。

Enter grades separated by commas:
92,A,96,94
I parsed these values: 92,0,96,94
The average grade is 70.5

要使用一个语句将字符串数组转换为整数数组，请使用LINQ。

int[] grades = parts.Select((part) => int.Parse(part)).ToArray();

这将是一个无效输入的例外。使上述内容与TryParse()一起使用非常棘手，但可行。

Answer 2

检查用户输入以避免因无效输入而导致的异常非常重要。以下是我将如何做到这一点：

class MainClass
{
    public static void Main(string[] args)
    {
        //Variable Declarations
        string response,
               name;

        string[] scores;

        int sumOfAllScores,
            scoreCount;

        bool validResponse;
        System.Text.RegularExpressions.Regex onlyDigits;

        //We need to assign response an initial value or else Visual Studio will complain
        //since it only receives its real value within a while loop (which as far as the parser is concerned
        //may or may not ever iterate.
        response = string.Empty;

        //Booleans are automatically assigned an intial value of 'false' but I like to intialize them anyway
        validResponse = false;

        //Initialize the score sum and score counter variables.
        sumOfAllScores = 0;
        scoreCount = 0;

        //This Regex pattern will allow us to inspect a string to ensure that it contains only digits.
        onlyDigits = new System.Text.RegularExpressions.Regex(@"^\d+$");

        Console.Write("Please enter your name: ");
        name = Console.ReadLine();
        Console.WriteLine("Hello, " + name);

        //This loop will iterate until the user provides valid input (comma-separated integers).
        while (!validResponse)
        {
            //When we enter the while loop, set validResponse to true.
            //If we encounter any invalid input from the user we will set this to false so that
            //the while loop will iterate again. 
            validResponse = true;

            Console.Write("What are your last three test scores (comma-separated list, please): ");
            response = Console.ReadLine();

            //Split response into an array of strings on the comma characters
            scores = response.Split(',');

            //Inspect each element of the string array scores and take action:
            foreach (string scoreEntry in scores)
            {
                //If the current array member being inspected consists of any characters that are not integers,
                //Complain to the user and break out of the foreach loop.  This will cause the while loop to iterate
                //again since validResponse is still false.
                if (!onlyDigits.IsMatch(scoreEntry))
                {
                    //Complain
                    Console.WriteLine("Invalid response. Please enter a comma-separated list of test scores");
                    Console.WriteLine(Environment.NewLine);

                    //Re-initialize the score sum and score count variables since we're starting over
                    sumOfAllScores = 0;
                    scoreCount = 0;

                    //Set validResponse to false and break out of the foreach loop
                    validResponse = false;
                    break;
                }

                //Otherwise, we have valid input, so we'll update our integer values
                else
                {
                    //Iterate the number of scores that have been entered and validated
                    scoreCount++;

                    //Use the static Convert class to convert scoreEntry to an Integer
                    //and add it to the score sum
                    sumOfAllScores += Convert.ToInt32(scoreEntry);
                }
            }
        }

        //Report the results to the user:
        Console.WriteLine("Your test scores are: " + response);
        Console.WriteLine("Your average score is " + sumOfAllScores / scoreCount);
    }
}

C＃初学者系统异常

2 个答案: