How can I create an enum which contains a slash?

Question

I want to have an enum like this but it complains that / is invalid.

public enum ImageMimeType

{

           img/bmp, img/jpeg

}

or how can I have an strongly typed array

List<string> myList = new List<string>{"img/bmp", img/jpeg"};

// myList.img/bmp is not possible either

Any way I can access this?

Answer 1

No, no cannot have a slash in the eanum value name - the name has to be conformant with the C# naming rules. The best you can do is decorate each enum value with a description attribute then map back and forth between the description and the enum value (the code below could be optimized to cache description/mime type mapping) :

 static class Program
    {
        public enum MimeType
        {
            Unknown,
            [Description("img/bmp")]
            ImageBmp,
            [Description("img/jpeg")]
            ImageJpeg
        }

        public static MimeType ToMimeTypeValue(this string value)
        {
            foreach (FieldInfo fi in typeof(MimeType).GetFields()) {
                if (!fi.IsStatic) {
                    continue;
                }

                object[] attrs = fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
                if (attrs == null || attrs.Length <= 0) {
                    continue;
                }

                DescriptionAttribute descr = (DescriptionAttribute)attrs[0];
                if (0 == string.Compare(value, descr.Description)) {
                    return (MimeType)fi.GetValue(null);
                }
            }

            return MimeType.Unknown;
        }

        public static string ToMimeTypeString(this MimeType value)
        {
            foreach (FieldInfo fi in typeof(MimeType).GetFields()) {
                if (!fi.IsStatic || (MimeType)fi.GetValue(null) != value) {
                    continue;
                }

                object[] attrs = fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
                if (attrs == null || attrs.Length <= 0) {
                    continue;
                }

                DescriptionAttribute descr = (DescriptionAttribute)attrs[0];
                return descr.Description;
            }

            return string.Empty;
        }

        static void Main(string[] args)
        {
            string stringValue = MimeType.ImageBmp.ToMimeTypeString();

            Console.WriteLine("{0} : {1}", MimeType.ImageBmp, stringValue);
            Console.WriteLine("{0} : {1}", stringValue, stringValue.ToMimeTypeValue());
        }
    }

HTH

Paul

Answer 2

You can't.  The "/" or the division operator is considered a mathematical symbol (Sm) as far as character classes in Unicode is concerned.  According to 2.4.2 of the C# spec, mathematical symbols are not allowed for identifiers in C#.  You might find something that works in OmegaMan's workaround. 

---

David Morton - http://blog.davemorton.net/ - @davidmmorton - ForumsBrowser, a WPF MSDN Forums Client

Answer 3

The notion of a "strongly typed array" that contains strings doesn't make sense.  You always need code to convert strings to enums.  Enum.GetNames() can help but in this case you should just write it explicitly:

    public enum ImageMimeType {
      imgBmp, imgJpeg
    }
    public static ImageMimeType MapImageType(string type) {
      switch (type.ToLower()) {
        case "img/bmp":  return ImageMimeType.imgBmp;
        case "img/jpeg": return ImageMimeType.imgJpeg;
        default: throw new ArgumentException("Invalid image type");
      }
    }

---

Hans Passant.