How do you map a DateTime property to 2 varchar columns in the database with NHibernate (Fluent)?

I'm dealing with a legacy database that has date and time fields as char(8) columns (formatted yyyyMMdd and HH:mm:ss, respectively) in some of the tables. How can i map the 2 char columns to a single .NET DateTime property? I have tried the following, but i get a "can't access setter" error of course because DateTime Date and TimeOfDay properties are read-only:

public class SweetPocoMannaFromHeaven
{    
    public virtual DateTime? FileCreationDateTime { get; set; }
}

.

mapping.Component<DateTime?>(x => x.FileCreationDateTime,
            dt =>
            {
                dt.Map(x => x.Value.Date,
                    "file_creation_date");
                dt.Map(x => x.Value.TimeOfDay,
                    "file_creation_time");
            });

I have also tried defining a IUserType for DateTime, but i can't figure it out. I've done a ton of googling for an answer, but i can't figure it out still. What is my best option to handle this stupid legacy database convention? A code example would be helpful since there's not much out for documentation on some of these more obscure scenarios.

You need an ICompositeUserType to handle more than one column. You need to beef up the error checking, parsing formats, etc, but here is a starting point for you.

HTH,
Berryl

public class LegacyDateUserType : ICompositeUserType
{

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

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

    public object NullSafeGet(IDataReader dr, string[] names, ISessionImplementor session, object owner)
    {
        if (dr == null) return null;

        var datePortion = NHibernateUtil.String.NullSafeGet(dr, names[0], session, owner) as string;
        var timePortion = NHibernateUtil.String.NullSafeGet(dr, names[1], session, owner) as string;

        var date = DateTime.Parse(datePortion);
        var time = DateTime.Parse(timePortion);
        return date.AddTicks(time.Ticks);
    }

    ///<summary>
    /// Write an instance of the mapped class to a prepared statement. Implementors 
    /// should handle possibility of null values. A multi-column type should be written 
    /// to parameters starting from index.
    ///</summary>
    public void NullSafeSet(IDbCommand cmd, object value, int index, ISessionImplementor session) {
        if (value == null) {
            // whatever
        }
        else {
            var date = (DateTime) value;
            var datePortion = date.ToString("your date format");
            NHibernateUtil.String.NullSafeSet(cmd, datePortion, index, session);
            var timePortion = date.ToString("your time format");
            NHibernateUtil.String.NullSafeSet(cmd, timePortion, index + 1, session);
        }
    }

    public object GetPropertyValue(object component, int property)
    {
        var date = (DateTime)component;
        return property == 0 ? date.ToString("your date format") : date.ToString("your time format");
    }

    public void SetPropertyValue(object component, int property, object value)
    {
        throw new NotSupportedException("DateTime is an immutable object.");
    }

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

    public object Disassemble(object value, ISessionImplementor session) { return value; }

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

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

    ///<summary>Get the "property names" that may be used in a query.</summary>
    public string[] PropertyNames { get { return new[] { "DATE_PORTION", "TIME_PORTION" }; } }

    ///<summary>Get the corresponding "property types"</summary>
    public IType[] PropertyTypes { get { return new IType[] { NHibernateUtil.String, NHibernateUtil.String }; } }

    ///<summary>The class returned by NullSafeGet().</summary>
    public Type ReturnedClass { get { return typeof(DateTime); } }

    ///<summary>Are objects of this type mutable?</summary>
    public bool IsMutable { get { return false; } }

}

=== fluent mapping (assuming automapping w/override classes) ====

 public void Override(AutoMapping<MyClass> m)
 {
     ....
     m.Map(x => x.MyDateTime).CustomType<LegacyDateUserType>();
 }