在流編寫器中使用for循環

Question

我正在嘗試創建具有多個屬性的問題對象，所有這些屬性都存儲在文本文件中，並使用StreamReader檢索。

一個屬性是數組Choices[] 。 我需要所說的數組能夠基於qType變量的值進行填充。

例如： if qType = "button" ，那么Choices[]應該只從文件讀取4行。 而if qType = "dragdrop"則Choices[]應該從文件中讀取6次。 到目前為止，我已經嘗試過使用for循環，case語句和if語句-所有這些都已中斷。 有人可以告訴我如何在不中斷StreamReader的情況下做到這一點嗎？

這是有效的代碼：

using (var quizFileReader = new System.IO.StreamReader("PhysQuestions.txt"))
{
    string line;
    Question question;

    // Loop through the lines of the file until there are no more (the ReadLine function return null at this point).
    // ReadLine called here only reads question texts (first line of a question), while other calls to ReadLine read the choices.
    while ((line = quizFileReader.ReadLine()) != null)
    {
        // Skip this loop if the line is empty.
        if (line.Length == 0)
            continue;

        // Create a new question object.
        // The "object initializer" construct is used here by including { } after the constructor to set variables.
        question = new Question()
        {
            // Set the question text to the line just read.
            QuestionText = line,
            qType = quizFileReader.ReadLine(),
            // Set the choices to an array containing the next 4 lines read from the file.
            Choices = new string[]
            { 
                quizFileReader.ReadLine(), 
                quizFileReader.ReadLine(),
                quizFileReader.ReadLine(),
                quizFileReader.ReadLine(),
            },

            hintTxt = quizFileReader.ReadLine(),
            difficulty = Convert.ToDouble(quizFileReader.ReadLine()),
            imgPath = quizFileReader.ReadLine()
        };
    }
}

這是我嘗試做的不起作用的事情：

Choices = new string[]
{ 
    for(int i=0; i<4; i++)
    {
        quizFileReader.ReadLine(), // expects a ;
    }
}, // excepts a ;

這是我正在使用的完整代碼：

    public string QuestionText, imgPath, hintTxt; // Actual question text.
    public string[] Choices;    // Array of answers from which user can choose.
    public int Answer, qNum, linesToRead;          // Index of correct answer within Choices.
    public double difficulty;  // Double that represents difficulty of each question

    public List<Question> getQues() // reads questions from text file, assigns all strings in text file to index of List, returns the full list of questions
    {
        // Create new list to store all questions.
        var questions = new List<Question>();

        // Open file containing quiz questions using StreamReader, which allows you to read text from files easily.
        using (var quizFileReader = new System.IO.StreamReader("PhysQuestions.txt"))
        {
            string line;
            Question question;

            // Loop through the lines of the file until there are no more (the ReadLine function return null at this point).
            // ReadLine called here only reads question texts (first line of a question), while other calls to ReadLine read the choices.
            while ((line = quizFileReader.ReadLine()) != null)
            {
                // Skip this loop if the line is empty.
                if (line.Length == 0)
                    continue;

                // Create a new question object.
                // The "object initializer" construct is used here by including { } after the constructor to set variables.
                question = new Question()
                {
                    // Set the question text to the line just read.
                    QuestionText = line,
                    linesToRead = Convert.ToInt32(quizFileReader.ReadLine()),
                    Choices = new string[linesToRead];
                     for (int i=0; i < linesToRead; i++)
                    {
                      Choices[i] = await quizFileReader.ReadLineAsync();
                    }


                     hintTxt = await quizFileReader.ReadLineAsync();
                    difficulty =  Convert.ToDouble(quizFileReader.ReadLine());
                    imgPath = quizFileReader.ReadLine();

                };

                // Set correct answer to -1, this indicates that no correct answer has been found yet.
                question.Answer = -1;

                // Check each choice to see if it begins with the '!' char (marked as correct).
                for (int i = 0; i < 4; i++)
                {
                    if (question.Choices[i].StartsWith("!"))
                    {
                        // Current choice is marked as correct. Therefore remove the '!' from the start of the text and store the index of this choice as the correct answer.
                        question.Choices[i] = question.Choices[i].Substring(1);
                        question.Answer = i;
                        break; // Stop looking through the choices.
                    }
                }

                // Check if none of the choices was marked as correct. If this is the case, we throw an exception and then stop processing.
                if (question.Answer == -1)
                {
                    throw new InvalidOperationException(
                        "No correct answer was specified for the following question.\r\n\r\n" + question.QuestionText);
                }






                // Finally, add the question to the complete list of questions.
                questions.Add(question);
            }

            return questions;
        }
    }

Answer 1

一旦知道要讀取多少行，便可以執行以下操作：

using (var quizFileReader = new System.IO.StreamReader("PhysQuestions.txt"))
{
    Question question;
    int linesToRead = 4;
    string[] choices = new string[linesToRead];

    for (int i=0; i < linesToRead; i++)
    {
        choices[i] = await quizFileReader.ReadLineAsync();
    }
}

那應該使您朝着正確的方向開始，但是如果您陷入困境，請告訴我。

我還將ReadLine轉換為它的異步版本，因此它不會被阻塞。