C#使用与常量名称匹配的变量调用常量

Question

我有一组const，然后我动态地创建一个变量，该变量等于const的一个名称。我需要调用const，我知道我可以使用if else语句，但我想知道是否有更好的方法，谢谢！

    public const int LifeBand1Standard = 78;
    public const int LifeBand1Multi = 61;
    public const int LifeBand2Standard = 71;
    public const int LifeBand2Multi = 56;
    public const int LifeBand3Standard = 62;
    public const int LifeBand3Multi = 48;
    public const int LifeBand4Standard = 56;
    public const int LifeBand4Multi = 44;
    public const int LifeBand5Standard = 45;
    public const int LifeBand5Multi = 35;

    // Band discounts/loads for trauma cover
    public const int TraumaBand1Standard = 140;
    public const int TraumaBand1Multi = 126;
    public const int TraumaBand2Standard = 135;
    public const int TraumaBand2Multi = 121;
    public const int TraumaBand3Standard = 121;
    public const int TraumaBand3Multi = 109;
    public const int TraumaBand4Standard = 110;
    public const int TraumaBand4Multi = 99;
    public const int TraumaBand5Standard = 100;
    public const int TraumaBand5Multi = 90;

    protected float GetPercentageFromBand(int band)
    {
        var constantName = "Life";

        if (IsTraumaCover == true)
        {
            constantName = "Trauma";
        }

        constantName += "Band" + band;

        if (IsMultiLife == true)
        {
            constantName += "Multi";
        }
        else
        {
            constantName += "Standard";
        }

        // Constant should look something like LifeBand3Standard and will return the value of the const LifeBand3Standard
        BandPercentage = InsuranceBandFetcher.constantName;

    }

Answer 1

使用与Dictionary结合使用的enum，如下所示(只是一个示例代码)

public enum MyConstant
{
    LifeBand1Standard = 78,
    LifeBand1Multi = 61,
    LifeBand2Standard = 71,
    LifeBand2Multi = 56,
    LifeBand3Standard = 62,
    LifeBand3Multi = 48
}

将数据保存在字典中

        Dictionary<string, MyConstant> dict = new Dictionary<string, MyConstant>
        {
            { "TraumaCover ", MyConstant.LifeBand3Multi},
            { "MultiLife ", MyConstant.LifeBand2Standard}
        };

        Console.WriteLine(dict["MultiLife "]);

根据您的评论，这是另一个示例代码。您可以使用Enum.Parse()实现此目的，如下所示

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            string key = PrepareConstant(1, false);
            MyConstant val = (MyConstant)Enum.Parse(typeof(MyConstant), key, true);

            Dictionary<string, MyConstant> dict = new Dictionary<string, MyConstant>
            {
                { key, val},
            };

            Console.WriteLine(dict[key]); // output: LifeBand1Standard

            Console.ReadKey();
        }

        static string PrepareConstant(int band, bool isMultiLife)
        {
            var constantName = "Life";
            constantName += "Band" + band;
            constantName += (isMultiLife) ?  "Multi" : "Standard";

            return constantName;
        }
    }

    public enum MyConstant
    {
        LifeBand1Standard = 78,
        LifeBand1Multi = 61,
        LifeBand2Standard = 71,
        LifeBand3Standard = 62,
        TrumaBand2Multi = 56,
        TrumaBand3Multi = 48
    }
}

Answer 2

使用字典，而不是魔术字符串(特别是以编程方式创建的字符串)。

我不理解您的业务域，所以我的枚举名称/值可能完全奇怪，但我将如何处理这个问题：

public enum Cover
{
    Life,
    Trauma
}

public enum MultiLife
{
    Multi,
    Standard
}

public readonly Dictionary<Tuple<Cover, int, MultiLife>, int> Values
 = new Dictionary<System.Tuple<UserQuery.Cover, int, UserQuery.MultiLife>, int>
 {
    [Tuple.Create(Cover.Life, 1, MultiLife.Standard)] = 78,
    [Tuple.Create(Cover.Life, 1, MultiLife.Multi)] = 61,
    [Tuple.Create(Cover.Life, 2, MultiLife.Standard)] = 71,
    // [...]
 };

那么用法应该是：

var bandPercentage
 = Values[Tuple.Create(IsTraumaCover ? Cover.Trauma : Cover.Life,
                       band,
                       IsMultiLife ? MultiLife.Multi : MultiLife.Standard)];

Answer 3

如果没有反思，你想要做的事情是不可能的。即使有反射，这也不是推荐的设计。

您似乎需要的是一个从三个值映射的函数: 1.多值或标准值(布尔值或枚举)。2.生命或创伤(布尔或枚举)。3. Number (int) (或byte，或自定义结构)，并返回某种类型的数字(百分比？)。

enum BandKind {
 Multi,
 Standard,
}

enum BandType {
 Life,
 Trauma
}

int GetBandValue(BandKind kind, BandType type, int num) {

/// impl here
}

好吧，那么如何实现GetBandValue呢？你可以使用嵌套的switch语句并返回字面值，这可能是一种选择，但嵌套的开关最终会变得有点丑陋。您可以创建一个多维数组，并使用这些值对其进行索引。

int[][][] BandData = {{{78, 61},{71, 56},...}}}; // build this array with your real values.

然后，您的实现可以是：

int GetBandValue(BandKind kind, BandType type, int num) {

    return BandData[(int)kind][(int)type][num];
}