Enum.HasFlag, why no Enum.SetFlag?

Question

I have to build an extension method for each flag type I declare, like so:

public static EventMessageScope SetFlag(this EventMessageScope flags, 
    EventMe         


        

Answer 1

public static class SomeEnumHelperMethodsThatMakeDoingWhatYouWantEasier
{
    public static T IncludeAll(this Enum value)
    {
        Type type = value.GetType();
        object result = value;
        string[] names = Enum.GetNames(type);
        foreach (var name in names)
        {
            ((Enum) result).Include(Enum.Parse(type, name));
        }

        return (T) result;
        //Enum.Parse(type, result.ToString());
    }

    /// 

    /// Includes an enumerated type and returns the new value
    /// 
    public static T Include(this Enum value, T append)
    {
        Type type = value.GetType();

        //determine the values
        object result = value;
        var parsed = new _Value(append, type);
        if (parsed.Signed is long)
        {
            result = Convert.ToInt64(value) | (long) parsed.Signed;
        }
        else if (parsed.Unsigned is ulong)
        {
            result = Convert.ToUInt64(value) | (ulong) parsed.Unsigned;
        }

        //return the final value
        return (T) Enum.Parse(type, result.ToString());
    }

    /// 

    /// Check to see if a flags enumeration has a specific flag set.
    /// 
    /// Flags enumeration to check
    /// Flag to check for
    /// 
    public static bool HasFlag(this Enum variable, Enum value)
    {
        if (variable == null)
            return false;

        if (value == null)
            throw new ArgumentNullException("value");

        // Not as good as the .NET 4 version of this function, 
        // but should be good enough
        if (!Enum.IsDefined(variable.GetType(), value))
        {
            throw new ArgumentException(string.Format(
                "Enumeration type mismatch.  The flag is of type '{0}', " +
                "was expecting '{1}'.", value.GetType(), 
                variable.GetType()));
        }

        ulong num = Convert.ToUInt64(value);
        return ((Convert.ToUInt64(variable) & num) == num);
    }


    /// 

    /// Removes an enumerated type and returns the new value
    /// 
    public static T Remove(this Enum value, T remove)
    {
        Type type = value.GetType();

        //determine the values
        object result = value;
        var parsed = new _Value(remove, type);
        if (parsed.Signed is long)
        {
            result = Convert.ToInt64(value) & ~(long) parsed.Signed;
        }
        else if (parsed.Unsigned is ulong)
        {
            result = Convert.ToUInt64(value) & ~(ulong) parsed.Unsigned;
        }

        //return the final value
        return (T) Enum.Parse(type, result.ToString());
    }

    //class to simplfy narrowing values between
    //a ulong and long since either value should
    //cover any lesser value
    private class _Value
    {
        //cached comparisons for tye to use
        private static readonly Type _UInt32 = typeof (long);
        private static readonly Type _UInt64 = typeof (ulong);

        public readonly long? Signed;
        public readonly ulong? Unsigned;

        public _Value(object value, Type type)
        {
            //make sure it is even an enum to work with
            if (!type.IsEnum)
            {
                throw new ArgumentException(
                    "Value provided is not an enumerated type!");
            }

            //then check for the enumerated value
            Type compare = Enum.GetUnderlyingType(type);

            //if this is an unsigned long then the only
            //value that can hold it would be a ulong
            if (compare.Equals(_UInt32) || compare.Equals(_UInt64))
            {
                Unsigned = Convert.ToUInt64(value);
            }
                //otherwise, a long should cover anything else
            else
            {
                Signed = Convert.ToInt64(value);
            }
        }
    }
}