c# - 如何将我的一些代码更改为类？

Question

我写了一些代码并且它可以工作，但现在尝试使用我的一些代码并将其更改为一个类。我已经将部分代码更改为首先是一个方法，然后将其变成一个类。但是代码的最后一部分无法弄清楚如何更改为一个方法，以便我可以创建一个类。

else if (input == "3")
{
    Console.WriteLine("Here are your Students: ");
    Array.Sort(names);
    Console.WriteLine(String.Join(", ", names));                    
    Console.WriteLine("");

    double average = gradesList.Average();

    if (average >= 90)
    {
        Console.WriteLine($"There average is a {average.ToString("n2")} which is an A.");

    }
    else if (average >= 80)
    {
        Console.WriteLine($"There average is a {average.ToString("n2")} which is an B.");
    }
    else if (average >= 70)
    {
        Console.WriteLine($"There average is a {average.ToString("n2")} which is an C.");
    }
    else if (average >= 60)
    {
        Console.WriteLine($"There average is a {average.ToString("n2")} which is an D.");
    }
    else
    {
        Console.WriteLine($"There average is a {average.ToString("n2")} which is an E.");
    }

}

我想离开第一部分，只是将成绩部分改为类(class)。我试过 public static string GetLetterGrade(int average) return ($"There average is a {average.ToString("n2")} which is an A.") 但得到各种我不理解的错误。

Answer 1

我会让成绩成为一个不可改变的结构。它代表一个值，应该是一个值类型。类是引用类型。

public readonly struct Grade
{
    public Grade(double percentage)
    {
        Percentage = percentage;
    }

    public double Percentage { get; }

    public char Letter
    {
        get {
            if (Percentage >= 90) return 'A';
            if (Percentage >= 80) return 'B';
            if (Percentage >= 70) return 'C';
            if (Percentage >= 60) return 'D';
            return 'E';
        }
    }

    public override string ToString() => $"{Percentage:n2} ({Letter})";
}

因为 if 语句返回，所以没有必要有 else 部分。

然后您可以轻松打印消息

double average = gradesList.Average();
var grade = new Grade(average);
Console.WriteLine(
    $"There average is a {grade.Percentage:n2} which is an {grade.Letter}.");

请注意，因为 ToString 被覆盖，所以您可以直接打印成绩。

Console.WriteLine($"The average grade is {grade}");

它将打印类似The average grade is 74.25 (C)的内容。