最后我选择了 ICompositeUserType。代码如下，
public class ColorType : ICompositeUserType
{
/// <summary>
/// Get the value of a property
/// </summary>
/// <param name="component">an instance of class mapped by this "type"</param>
/// <param name="property"/>
/// <returns>
/// the property value
/// </returns>
public object GetPropertyValue(object component, int property)
{
var color = (Color) component;
if (property == 0)
{
return color.ToArgb();
}
return (int) color.ToKnownColor();
}
/// <summary>
/// Set the value of a property
/// </summary>
/// <param name="component">an instance of class mapped by this "type"</param>
/// <param name="property"/>
/// <param name="value">the value to set</param>
public void SetPropertyValue(object component, int property, object value)
{
throw new InvalidOperationException("Color is immutable");
}
/// <summary>
/// Compare two instances of the class mapped by this type for persistence
/// "equality", ie. equality of persistent state.
/// </summary>
/// <param name="x"/><param name="y"/>
/// <returns/>
public new bool Equals(object x, object y)
{
return ReferenceEquals(x, y) ||
x != null && y != null &&
object.Equals(x, y);
}
/// <summary>
/// Get a hashcode for the instance, consistent with persistence "equality"
/// </summary>
public int GetHashCode(object x)
{
return x == null
? 0
: x.GetHashCode();
}
/// <summary>
/// Retrieve an instance of the mapped class from a IDataReader. Implementors
/// should handle possibility of null values.
/// </summary>
/// <param name="dr">IDataReader</param>
/// <param name="names">the column names</param>
/// <param name="session"/>
/// <param name="owner">the containing entity</param>
/// <returns/>
public object NullSafeGet(IDataReader dr, string[] names,
ISessionImplementor session, object owner)
{
var argb = (int?) NHibernateUtil.Int32.NullSafeGet(dr, names[0]);
var knownColor = (int?) NHibernateUtil.Int32.NullSafeGet(dr, names[1]);
return knownColor != null
? Color.FromKnownColor((KnownColor) knownColor.Value)
: Color.FromArgb(argb.Value);
}
/// <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.
/// If a property is not settable, skip it and don't increment the index.
/// </summary>
/// <param name="cmd"/>
/// <param name="value"/>
/// <param name="index"/>
/// <param name="settable"/>
/// <param name="session"/>
public void NullSafeSet(IDbCommand cmd, object value, int index,
bool[] settable, ISessionImplementor session)
{
var color = (Color) value;
if (color.IsKnownColor)
{
((IDataParameter) cmd.Parameters[index]).Value = DBNull.Value;
((IDataParameter) cmd.Parameters[index + 1]).Value = (int) color.ToKnownColor();
}
else
{
((IDataParameter) cmd.Parameters[index]).Value = color.ToArgb();
((IDataParameter) cmd.Parameters[index + 1]).Value = DBNull.Value;
}
}
/// <summary>
/// Return a deep copy of the persistent state, stopping at entities and at collections.
/// </summary>
/// <param name="value">generally a collection element or entity field</param>
/// <returns/>
public object DeepCopy(object value)
{
return value;
}
/// <summary>
/// Transform the object into its cacheable representation.
/// At the very least this method should perform a deep copy.
/// That may not be enough for some implementations,
/// method should perform a deep copy. That may not be enough for
/// some implementations, however; for example, associations must
/// be cached as identifier values. (optional operation)
/// </summary>
/// <param name="value">the object to be cached</param>
/// <param name="session"/>
/// <returns/>
public object Disassemble(object value, ISessionImplementor session)
{
return value;
}
/// <summary>
/// Reconstruct an object from the cacheable representation.
/// At the very least this method should perform a deep copy. (optional operation)
/// </summary>
/// <param name="cached">the object to be cached</param>
/// <param name="session"/>
/// <param name="owner"/>
/// <returns/>
public object Assemble(object cached, ISessionImplementor session, object owner)
{
return cached;
}
/// <summary>
/// During merge, replace the existing (target) value in the entity we are merging to
/// with a new (original) value from the detached entity we are merging. For immutable
/// objects, or null values, it is safe to simply return the first parameter. For
/// mutable objects, it is safe to return a copy of the first parameter. However, since
/// composite user types often define component values, it might make sense to recursively
/// replace component values in the target object.
/// </summary>
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[] {"Argb", "KnownColor"}; } }
/// <summary>
/// Get the corresponding "property types"
/// </summary>
public IType[] PropertyTypes
{
get
{
return new IType[]
{
NHibernateUtil.Int32, NHibernateUtil.Int32
};
}
}
/// <summary>
/// The class returned by NullSafeGet().
/// </summary>
public Type ReturnedClass { get { return typeof (Color); } }
/// <summary>
/// Are objects of this type mutable?
/// </summary>
public bool IsMutable { get { return false; } }
}