用于状态处理的多态Enum

Question

如何在不使用C#中的switch或if语句的情况下处理枚举？

例如

enum Pricemethod
{
    Max,
    Min,
    Average
}

......我有一篇文章

 public class Article 
{
    private List<Double> _pricehistorie;

    public List<Double> Pricehistorie
    {
        get { return _pricehistorie; }
        set { _pricehistorie = value; }
    }

    public Pricemethod Pricemethod { get; set; }

    public double Price
    {
        get {
            switch (Pricemethod)
            {
                case Pricemethod.Average: return Average();
                case Pricemethod.Max: return Max();
                case Pricemethod.Min: return Min();
            }

        }
    }

}

我想避免使用switch语句并使其成为通用语句.

对于特定的Pricemethod,请调用特定的计算并将其返回.

get { return CalculatedPrice(Pricemethod); }

这里使用的模式可能有人有一个很好的实现想法.已经搜索了状态模式,但我不认为这是正确的.

Answer 1

我该如何处理枚举不使用switch或if在C#中的语句？

你没有.枚举只是一种令人愉快的写作语法const int.

考虑这种模式:

public abstract class PriceMethod
{
  // Prevent inheritance from outside.
  private PriceMethod() {}

  public abstract decimal Invoke(IEnumerable<decimal> sequence);

  public static PriceMethod Max = new MaxMethod();

  private sealed class MaxMethod : PriceMethod
  {
    public override decimal Invoke(IEnumerable<decimal> sequence)
    {
      return sequence.Max();
    }
  }

  // etc, 
}

现在你可以说

public decimal Price
{
    get { return PriceMethod.Invoke(this.PriceHistory); }
}

用户可以说

myArticle.PriceMethod = PriceMethod.Max;
decimal price = myArticle.Price;

Answer 2

您可以创建一个interface和class实现它的es:

public interface IPriceMethod
{
    double Calculate(IList<double> priceHistorie);
}
public class AveragePrice : IPriceMethod
{
    public double Calculate(IList<double> priceHistorie)
    {
        return priceHistorie.Average();
    }
}
// other classes
public class Article 
{
    private List<Double> _pricehistorie;

    public List<Double> Pricehistorie
    {
        get { return _pricehistorie; }
        set { _pricehistorie = value; }
    }

    public IPriceMethod Pricemethod { get; set; }

    public double Price
    {
        get {
            return Pricemethod.Calculate(Pricehistorie);
        }
    }

}

编辑:另一种方法是使用a Dictionary来映射Funcs,所以你不必为此创建类(这段代码基于Servy的代码,自从删除了他的答案):

public class Article
{
    private static readonly Dictionary<Pricemethod, Func<IEnumerable<double>, double>>
        priceMethods = new Dictionary<Pricemethod, Func<IEnumerable<double>, double>>
        {
            {Pricemethod.Max,ph => ph.Max()},
            {Pricemethod.Min,ph => ph.Min()},
            {Pricemethod.Average,ph => ph.Average()},
        };

    public Pricemethod Pricemethod { get; set; }
    public List<Double> Pricehistory { get; set; }

    public double Price
    {
        get
        {
            return priceMethods[Pricemethod](Pricehistory);
        }
    }
}