c# - リフレクションによって型のすべての定数を取得するにはどうすればよいですか?

Question

リフレクションを使用して任意の型のすべての定数を取得するにはどうすればよいですか?

Answer 1

古いコードですが：

private FieldInfo[] GetConstants(System.Type type)
{
    ArrayList constants = new ArrayList();

    FieldInfo[] fieldInfos = type.GetFields(
        // Gets all public and static fields

        BindingFlags.Public | BindingFlags.Static | 
        // This tells it to get the fields from all base types as well

        BindingFlags.FlattenHierarchy);

    // Go through the list and only pick out the constants
    foreach(FieldInfo fi in fieldInfos)
        // IsLiteral determines if its value is written at 
        //   compile time and not changeable
        // IsInitOnly determines if the field can be set 
        //   in the body of the constructor
        // for C# a field which is readonly keyword would have both true 
        //   but a const field would have only IsLiteral equal to true
        if(fi.IsLiteral && !fi.IsInitOnly)
            constants.Add(fi);           

    // Return an array of FieldInfos
    return (FieldInfo[])constants.ToArray(typeof(FieldInfo));
}

ソース

ジェネリックと LINQ を使用して、よりクリーンなコードに簡単に変換できます。

private List<FieldInfo> GetConstants(Type type)
{
    FieldInfo[] fieldInfos = type.GetFields(BindingFlags.Public |
         BindingFlags.Static | BindingFlags.FlattenHierarchy);

    return fieldInfos.Where(fi => fi.IsLiteral && !fi.IsInitOnly).ToList();
}

または1行で：

type.GetFields(BindingFlags.Public | BindingFlags.Static |
               BindingFlags.FlattenHierarchy)
    .Where(fi => fi.IsLiteral && !fi.IsInitOnly).ToList();

Answer 2

特定の型のすべての定数の値をターゲット型から取得したい場合は、拡張メソッドを次に示します (このページの回答の一部を拡張します)。

public static class TypeUtilities
{
    public static List<T> GetAllPublicConstantValues<T>(this Type type)
    {
        return type
            .GetFields(BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy)
            .Where(fi => fi.IsLiteral && !fi.IsInitOnly && fi.FieldType == typeof(T))
            .Select(x => (T)x.GetRawConstantValue())
            .ToList();
    }
}

次に、このようなクラスの場合

static class MyFruitKeys
{
    public const string Apple = "apple";
    public const string Plum = "plum";
    public const string Peach = "peach";
    public const int WillNotBeIncluded = -1;
}

string次のように定数値を取得できます。

List<string> result = typeof(MyFruitKeys).GetAllPublicConstantValues<string>();
//result[0] == "apple"
//result[1] == "plum"
//result[2] == "peach"

Answer 3

値を取得するために使用property.GetConstantValue()します。

Answer 4

public class Constants
{
    public class InputType
    {
        public const string DOCUMENTPHOTO = "document-photo";
        public const string SELFIEPHOTO = "selfie-photo";
        public const string SELFIEVIDEO = "selfie-video";
        public static List<string> Domain { get { return typeof(Constants.InputType).GetAllPublicConstantValues<string>(); } }
    }
    public class Type
    {
        public const string DRIVINGLICENSE = "driving-license";
        public const string NATIONALID = "national-id";
        public const string PASSPORT = "passport";
        public const string PROOFOFRESIDENCY = "proof-of-residency";
        public static List<string> Domain { get { return typeof(Constants.Type).GetAllPublicConstantValues<string>(); } }
    }
    public class Page
    {
        public const string FRONT = "front";
        public const string BLACK = "back";
        public static List<string> Domain { get { return typeof(Constants.Page).GetAllPublicConstantValues<string>(); } }
    }
    public class FileType
    {
        public const string FRONT = "selfie";
        public const string BLACK = "video";
        public const string DOCUMENT = "document";
        public const string MEDIA = "media";
        public const string CAPTCHA = "captcha";
        public const string DIGITALSIGNATURE = "digitalSignature";
        public static List<string> Domain { get { return typeof(Constants.FileType).GetAllPublicConstantValues<string>(); } }
    }
}

public static class TypeUtilities
{
    public static List<T> GetAllPublicConstantValues<T>(this Type type)
    {
        return type
            .GetFields(BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy)
            .Where(fi => fi.IsLiteral && !fi.IsInitOnly && fi.FieldType == typeof(T))
            .Select(x => (T)x.GetRawConstantValue())
            .ToList();
    }
}

使用: var inputTypeDomain = Constants.InputType.Domain;