Enum, Alternate Values, and FluentNhibernate

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

using NHibernate.UserTypes;
using NHibernate.SqlTypes;

using Common;


namespace FluentNHibernateEnum.UnitTests.MapHelpers
{
    /// <summary>
    /// Mape EnumKey attribute to database
    /// </summary>
    /// <example>Map(x =&gt; x.ActivityType).CustomType&lt;EnumKeyMapping&lt;ActivityType&gt;&gt;().Column("ActivityType").Not.Nullable(); </example>
    /// <remarks> spinoff from http://stackoverflow.com/questions/1345426/fluent-nhibernate-table-per-hierarchy-mapping-problem by DaeMoon</remarks>
    /// <typeparam name="T"></typeparam>
    public class EnumKeyMapDescriptionHelper<T> : IUserType
    {

        private Int16 _length;

        public EnumKeyMapDescriptionHelper()
        {
            _length = 255;
        }

        public EnumKeyMapDescriptionHelper(Int16 length)
        {
            _length = length;
        }

        #region IUserType Members
        public object Assemble(object cached, object owner)
        { return cached; }
        public object DeepCopy(object value)
        { return value; }
        public object Disassemble(object value)
        { return value; }
        public int GetHashCode(object x)
        { return x.GetHashCode(); }
        public bool IsMutable
        {
            get { return false; }
        }
        public new bool Equals(object x, object y)
        { return object.Equals(x, y); }
        public object NullSafeGet(System.Data.IDataReader rs, string[] names, object owner)
        {
            int index0 = rs.GetOrdinal(names[0]);
            if (rs.IsDBNull(index0))
            { return null; }
            string description = rs.GetString(index0);
            return EnumExtension.EnumParseDescription<T>(description, true);
        }
        /// <summary>
        /// Use the enum value to get the description
        /// </summary>
        /// <param name="cmd"></param>
        /// <param name="value"></param>
        /// <param name="index"></param>
        public void NullSafeSet(System.Data.IDbCommand cmd, object value, int index)
        {
            if (value == null)
            {
                ((IDbDataParameter)cmd.Parameters[index]).Value = DBNull.Value;
            }
            else
            {
                T enumValue = (T)Enum.Parse(typeof(T), value.ToString());
                //((IDbDataParameter)cmd.Parameters[index]).Value = enumValue.GetKey();; //can't use cause don't know kind of type
                ((IDbDataParameter)cmd.Parameters[index]).Value = enumValue.GetDescription<T>();
                
            }
        }
        public object Replace(object original, object target, object owner)
        { return original; }
        public Type ReturnedType
        { get { return typeof(T); } }
        public global::NHibernate.SqlTypes.SqlType[] SqlTypes
        {
            //get { return new SqlType[] { SqlTypeFactory.GetString(4096) }; }
            get { return new SqlType[] { SqlTypeFactory.GetAnsiString(_length) }; }
        }

        #endregion
    }

}