C# 限制派生中枚举的选项 class

Question

所以我试图限制我在基础 class 中声明的枚举的选项，我可以 select 在派生的 class.

namespace FLYNET.Personeel
{
    public enum Graad
    {
        Captain,
        SeniorFlightOfficer,
        SecondOfficer,
        JuniorFlightOfficer,
        Steward,
        Purser
    };

public abstract class VliegendPersoneelslid : Personeelslid
{
    public VliegendPersoneelslid()
    {
    }

    public override decimal BerekenTotaleKostprijsPerDag()
    {
        return BasisKostprijsPerDag;
    }

    public List<Certificaat> Certificaten { get; set; }
}

以上是我试图从基础 class 员工那里使用的枚举。在派生的 class Cabincrew 中，我想限制可以在构造函数中 selected 的选项。如果错误的选项是selected，需要抛出指定的异常，所以有点像这样：

namespace FLYNET.Personeel
{
    public class CockpitPersoneel : VliegendPersoneelslid
    {
        public int VliegUren { get; set; }

        public Graad Graad { get; set; }


            public CockpitPersoneel()
            {
                if (Grade = Graad.Steward || Grade = Graad.Purser)
                {
                    throw new Exception 
                }
            }

            public override decimal BerekenTotaleKostprijsPerDag()
            {
                decimal kostprijsPersoneel = 0m;
                decimal percentage;

                return kostprijsPersoneel;
            }
        }
    }

我知道这可能是初学者的问题（确实是 :p），但请多多包涵。

Answer 1

我建议使用扩展方法来隐藏选项

public enum Grade {
   None, // <- zero option is often a good idea to include 
   Captain,
   SeniorFlightOfficer,
   SecondOfficer,
   JuniorFlightOfficer,
   Steward,
   Purser };

public static class GradeExtensions { 
  public static bool IsCabinCrue(this Grade grade) {
    return grade == Grade.Steward || grade == Grade.Purser;
  }

  public static bool IsCockpitPersonnel(this Grade grade) {
    return grade == Grade.Captain || 
           grade == Grade.SeniorFlightOfficer ||
           grade == Grade.SecondOfficer ||
           grade == Grade.JuniorFlightOfficer;
  } 
}

然后当验证 Grade 提供的值时，您可以使用扩展方法，就好像它们是枚举方法一样：

public class CabinCrue {
  ...
  public CabinCrue(Grade grade) {
    // Validation: Cabin Crue grade only
    // not Exception but ArgumentException: it's argument grade that's wrong
    if (!grade.IsCabinCrue()) 
      throw new ArgumentException("Cabin crue only", "grade");

    Grade = grade;

    ...
  } 

  public Grade Grade {
    get;
    private set;
  }
  ...
}

Answer 2

我觉得你逻辑有问题。您正在尝试验证构造函数中的 Grade 或 Graad。在构造函数调用之前不能设置属性 Graad。您的验证将检查变量 Graad 的默认值（在您的情况下为 Captain）。

您需要将 Graad 传递给构造函数才能进行验证：

public CockpitPersoneel(Graad g)
{
    if (g = Graad.Steward || g = Graad.Purser)
    {
        throw new Exception("wrong choice");
    }
    else
    {
        this.Graad = g;
    }
}

您还可以将验证逻辑直接放入完整属性并在那里抛出异常：

Graad _myGrade;

public Graad GradeOfPerson
{
    get { return _myGrade; }
    set
    {
        if (value = Graad.Steward || value = Graad.Purser)
        {
            throw new Exception("Not Allowed");

        }
        _myGrade = value; 
    }
}

这样您就可以将构造函数留空：

public CockpitPersoneel()
{
}

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