NHibernate StringToEnum abstract class (Allows you to store an enum as a string)

StringToEnum.cs

#region Namespaces

using System;
using System.Data;

using NHibernate;
using NHibernate.SqlTypes;
using NHibernate.UserTypes;

#endregion

public abstract class StringToEnum<T> : IUserType
    where T : struct, IConvertible
{
    protected StringToEnum()
    {
        if (!typeof(T).IsEnum)
        {
            throw new ArgumentException("T must be an enumerated type");
        }
    }

    public new bool Equals(object x, object y)
    {
        if (ReferenceEquals(x, y))
        {
            return true;
        }
        if (ReferenceEquals(null, x) || ReferenceEquals(null, y))
        {
            return false;
        }
        return x.Equals(y);
    }

    public int GetHashCode(object x)
    {
        return x == null ? typeof(T).GetHashCode() + 473 : x.GetHashCode();
    }

    public object DeepCopy(object value)
    {
        return value;
    }

    public object Replace(object original, object target, object owner)
    {
        return original;
    }

    public object Assemble(object cached, object owner)
    {
        return cached;
    }

    public object Disassemble(object value)
    {
        return value;
    }

    public SqlType[] SqlTypes
    {
        get
        {
            return new[] { NHibernateUtil.String.SqlType };
        }
    }

    public Type ReturnedType
    {
        get
        {
            return typeof(T);
        }
    }

    public bool IsMutable
    {
        get
        {
            return false;
        }
    }

    public object NullSafeGet(IDataReader rs, string[] names, object owner)
    {
        var obj = (string)NHibernateUtil.String.NullSafeGet(rs, names[0]);

        if (obj == null)
        {
            return null;
        }

        return ParseTo(obj);
    }

    public void NullSafeSet(IDbCommand cmd, object value, int index)
    {
        if (value == null)
        {
            ((IDataParameter)cmd.Parameters[index]).Value = DBNull.Value;
        }
        else
        {
            ((IDataParameter)cmd.Parameters[index]).Value = ParseFrom((T)value);
        }
    }

    protected abstract T ParseTo(string s);

    protected abstract string ParseFrom(T s);
}