创建复杂的数据结构

Question

我正在尝试通过创建一个小测验应用程序来自学 c#（asp.net 核心），但我对如何创建复杂的数据模型感到困惑。 想象一个包含如下问题集合的测验模型：

    public class Quiz
    {
       public int Id { get; set; }
       public Icollection<Question> Questions { get; set; }
    }

但是，如果我想要不同类型的问题（多项选择、真/假、文本答案...）我可以使用继承来缩短某些内容，还是我只需要为每种类型的问题创建不同的模型并输入他们是这样的：

Public class Quiz
{
   public Icollection<MultipleChoicQuestion> Questions { get; set; }
   public Icollection<TrueOrFalseQuestion> Questions { get; set; }
   public Icollection<TextQuestion> Questions { get; set; }
}

Answer 1

这个问题与 .NET Core 或 EF 并不完全相关，正如您所标记的，它与数据建模有关。

对于那些有点不同类型的模型，我建议你做如下。

这是Quiz 模型。

public class Quiz
{
    public int Id { get; set; }
    public List<Question> Questions { get; set; }
}

枚举问题

public class Question
{
    public int Id { get; set; }

    public QuestionType Type { get; set; }

    public List<Answer> Answers { get; set; }
}

public enum QuestionType
{
    MultipleChoice,
    TrueFalse,
    Text
}

最后一个Answers

public class Answer
{
    public int Id { get; set; }

    public int QuestionId { get; set; } 

    public Question Question { get; set; }

    public bool IsCorrect { get; set; }

    public string Value { get; set; }
}

这样，应用层将处理所有进程，但您将非常容易地存储数据。

对于MultipleChoice 问题，您添加多个答案并设置正确的IsCorrect = true。

对于TrueFalse，只添加2个答案并将IsCorrect = true设置为正确。

对于Text，只添加1个答案并设置IsCorrect = true。

Answer 2

一种方法是创建一个IQuestion 接口，其中包含运行测验所需的所有面向公众的方法和属性：

public interface IQuestion
{
    void AskQuestion();
    string CorrectAnswer { get; }
    bool IsCorrect { get; }
}

那么你可以在你的Quiz类中拥有这个接口的集合：

public class Quiz
{
    public ICollection<IQuestion> Questions { get; set; }
}

现在我们可以创建单独的类，每个类都以自己的方式实现IQuestion 属性和方法。

例如：

public class TextQuestion : IQuestion
{
    public bool IsCorrect => string.Equals(_userAnswer?.Trim(), CorrectAnswer?.Trim(),
        StringComparison.OrdinalIgnoreCase);

    public string CorrectAnswer { get; }

    private readonly string _question;
    private string _userAnswer;

    public TextQuestion(string question, string answer)
    {
        _question = question;
        CorrectAnswer = answer;
    }

    public void AskQuestion()
    {
        Console.WriteLine(_question);
        _userAnswer = Console.ReadLine();
    }
}

public class MultipleChoiceQuestion : IQuestion
{
    public bool IsCorrect => _userIndex == _correctIndex + 1;

    public string CorrectAnswer => (_correctIndex + 1).ToString();

    private readonly string _question;
    private readonly List<string> _choices;
    private readonly int _correctIndex;
    private int _userIndex;

    public MultipleChoiceQuestion(string question, List<string> choices, int correctIndex)
    {
        _question = question;
        _choices = choices;
        _correctIndex = correctIndex;
    }

    public void AskQuestion()
    {
        Console.WriteLine(_question);

        for (var i = 0; i < _choices.Count; i++)
        {
            Console.WriteLine($"{i + 1}: {_choices[i]}");
        }

        _userIndex = GetIntFromUser($"Answer (1 - {_choices.Count}): ",
            i => i > 0 && i <= _choices.Count);
    }

    private static int GetIntFromUser(string prompt, Func<int, bool> validator = null)
    {
        int result;

        do
        {
            Console.Write(prompt);
        } while (!int.TryParse(Console.ReadLine(), out result) &&
                 (validator == null || validator.Invoke(result)));

        return result;
    }
}

public class TrueOrFalseQuestion : IQuestion
{
    public bool IsCorrect => _userAnswer == _correctAnswer;

    public string CorrectAnswer => _correctAnswer.ToString();

    private readonly string _question;
    private readonly bool _correctAnswer;
    private bool _userAnswer;

    public TrueOrFalseQuestion(string question, bool correctAnswer)
    {
        _question = question;
        _correctAnswer = correctAnswer;
    }

    public void AskQuestion()
    {
        _userAnswer = GetBoolFromUser(_question + " (true/false)");
    }

    private static bool GetBoolFromUser(string prompt)
    {
        bool result;

        do
        {
            Console.Write(prompt + ": ");
        } while (!bool.TryParse(Console.ReadLine(), out result));

        return result;
    }
}

使用示例

static void Main()
{
    var quiz = new Quiz
    {
        Questions = new List<IQuestion>
        {
            new MultipleChoiceQuestion("Which color is also a fruit?",
                new List<string> {"Orange", "Yellow", "Green"}, 0),
            new TextQuestion("What is the last name of our first president?", 
                "Washington"),
            new TrueOrFalseQuestion("The day after yesterday is tomorrow", false),
        }
    };

    foreach (var question in quiz.Questions)
    {
        question.AskQuestion();
        Console.WriteLine(question.IsCorrect
            ? "Correct!\n"
            : $"The correct answer is: {question.CorrectAnswer}\n");
    }

    Console.WriteLine("Your final score is: " +
        $"{quiz.Questions.Count(q => q.IsCorrect)}/{quiz.Questions.Count}");

    GetKeyFromUser("\nPress any key to exit...");
}