Is it possible to create a generic bitwise enumeration 'IsOptionSet()' method?

Question

The below code makes it easy to pass in a set HtmlParserOptions and then check against a single option to see if it's been selected.

[Flags]
public enum HtmlParserOptions
{
    NotifyOpeningTags = 1,
    NotifyClosingTags = 2,
    NotifyText = 4,
    NotifyEmptyText = 8
}

private bool IsOptionSet(HtmlParserOptions options, HtmlParserOptions singleOption)
{
    return (options & singleOption) == singleOption;
}

My question is, is it possible to create a Generic version of this (I'm guessing through implementing an interface on the method properties) that will work with any enumeration with the Flags attribute?

Answer 1

Edit:

The easiest, nicest option is to upgrade to VS2010 Beta2 and use .NET 4's Enum.HasFlag method. The framework team has added a lot of nice additions to Enum to make them nicer to use.

---

Original (for current .NET):

You can do this by passing Enum, instead of generics:

static class EnumExtensions
{
    private static bool IsSignedTypeCode(TypeCode code)
    {
        switch (code)
        {
            case TypeCode.Byte:
            case TypeCode.UInt16:
            case TypeCode.UInt32:
            case TypeCode.UInt64:
                return false;
            default:
                return true;
        }
    }

    public static bool IsOptionSet(this Enum value, Enum option)
    {
        if (IsSignedTypeCode(value.GetTypeCode()))
        {
            long longVal = Convert.ToInt64(value);
            long longOpt = Convert.ToInt64(option);
            return (longVal & longOpt) == longOpt;
        }
        else
        {
            ulong longVal = Convert.ToUInt64(value);
            ulong longOpt = Convert.ToUInt64(option);
            return (longVal & longOpt) == longOpt;
        }
    }
}

This works perfectly, like so:

class Program
{
    static void Main(string[] args)
    {
        HtmlParserOptions opt1 = HtmlParserOptions.NotifyText | HtmlParserOptions.NotifyEmptyText;
        Console.WriteLine("Text: {0}", opt1.IsOptionSet(HtmlParserOptions.NotifyText));
        Console.WriteLine("OpeningTags: {0}", opt1.IsOptionSet(HtmlParserOptions.NotifyOpeningTags));

        Console.ReadKey();
    } 
}

THe above prints:

Text: True
OpeningTags: False

The downside to this, though, is it doesn't protect you from passing two different types of Enum types into the routine. You have to use it reasonably.