How can i get enum to contain a dash (-)?

You can't. Full stop. However, there are workarounds. You can, e.g., use DescriptionAttribute:

public enum PackageMedium : int {
    NTP,
    DAT,
    Exabyte,
    [Description("CD-ROM")]
    CDROM,
    DLT,
    D1,
    DVD,
    BD,
    LTO,
    LTO2,
    LTO4
}

This means, unfortunately, that you have more work to do when mapping values. On the other hand, it at lest compiles.

If you don't like that, pick another workaround, e.g., a dictionary:

var dict = Enum.GetValues(typeof(PackageMedium))
               .Cast<PackageMedium>()
               .Select(v => Tuple.Create(v == PackageMedium.CDROM ? "CD-ROM" : v.ToString(), v))
               .ToDictionary(t => t.Item1, t => t.Item2);

var myEnumVal = dict["CD-ROM"];

I know this is late, but this can be usefull.

Another workaround is to use the XmlEnumAttribute :

public enum PackageMedium : int {
NTP,
DAT,
Exabyte,
[XmlEnumAttribute("CD-ROM")]
CDROM,
DLT,
D1,
DVD,
BD,
LTO,
LTO2,
LTO4
}

It is used to validate an xml with an xsd. No additional code needed.

Short answer: No.

The reason being is that the - character is used as a token by the lexer for other purposes such as representing the binary and unary minus operator.

Your best bet is to either remove the - or replace it with some other character that is a valid character in identifier names. The only non-letter character you can generally use is _.

You can find more information in the C# Specification.