Fluent Nhibernate mapping to different columns by condition

Question

I have an a date table what contains some columns: INTEGER_VALUE, DOUBLE_VALUE, STRING_VALUE, DATETIME_VALUE

An object is:

public class Property
{
    public virtual int Id { set; get; }
    public virtual PropertyKind Kind { set; get; }
    public virtual object Value { set; get; }
    public PropertyValueType ValueType { set; get; }
}

PropertyValueType is:

public enum PropertyValueType
{
    TypeInt,
    TypeString,
    TypeDouble,
    TypeDateTime
}

The target is to map Value to different column of Database (firebird) condition to ValueType. For example if ValueType is TypeString we need to map it to STRING_VALUE column etc. ValueType sets while object begin created (in constructor) and never be changed. Is it possible? Or may be another solution?

Answer 1

NHibernate could help us to map Tables into C# objects / entities ( ORM ) . That means:

we should properly map ALL table's columns into ALL C# entity properties.

Later (eg business layer or inside of the get and set ) we should apply some validation rules to achieve required behaviour. Also we should extend the application tier to assure that for each kind of enum PropertyValueType , correct Property is filled, and will be persisted in a proper Column.

So the object structure could be like this

public class Property
{
    public virtual int Id { set; get; }
    public virtual PropertyKind Kind { set; get; }
    public PropertyValueType ValueType { set; get; }

    // not mapped
    public virtual object Value { ... some logic inside of the getter and setter }


    // mapped properties - could be protected and hidden from upper consumers
    protected virtual int?      IntValue      { get; set;}
    protected virtual string    StringValue   { get; set;}
    protected virtual double?   DoubleValue   { get; set;}
    protected virtual DateTime? DateTimeValue { get; set;}
}

So, NHibernate will help us to mapp columns and properties 1:1. The remaining handling is up to our application.

At the end this will bring us a lot, because we can issue even OrderBy accross all rows, while only some of them do have the column filled...