using System;
using NHibernate.Validator.Constraints;

namespace FormulaTests.Domain
{
   public class User
   {
       public virtual int Id { get; set; }

       [NotNull]
       public virtual DateTime JoinDate { set; get; }

       [NotNullNotEmpty]
       [Length(450)]
       public virtual string FirstName { get; set; }

       [NotNullNotEmpty]
       [Length(450)]
       public virtual string LastName { get; set; }

       [Length(900)]
       public virtual string FullName { get; private set; } //از طریق تعریف فرمول مقدار دهی می‌گردد

       public virtual int DayOfWeek { get; private set; }//از طریق تعریف فرمول مقدار دهی می‌گردد
   }
}

using FluentNHibernate.Automapping;
using FluentNHibernate.Automapping.Alterations;

namespace FormulaTests.Domain
{
   public class UserCustomMappings : IAutoMappingOverride<User>
   {
       public void Override(AutoMapping<User> mapping)
       {
           mapping.Id(u => u.Id).GeneratedBy.Identity(); //ضروری است 
           mapping.Map(x => x.DayOfWeek).Formula("DATEPART(dw, JoinDate) - 1");
           mapping.Map(x => x.FullName).Formula("FirstName + ' ' + LastName");
       }
   }
}

    create table Users (
       UserId INT IDENTITY NOT NULL,
      JoinDate DATETIME not null,
      FirstName NVARCHAR(450) not null,
      LastName NVARCHAR(450) not null,
      primary key (UserId)
   )

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
 default-access="property" auto-import="true" default-cascade="none" default-lazy="true">
 <class xmlns="urn:nhibernate-mapping-2.2" mutable="true"
 name="FormulaTests.Domain.User, FormulaTests, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="Users">
   <id name="Id" type="System.Int32" unsaved-value="0">
     <column name="UserId" />
     <generator class="identity" />
   </id>
   <property name="DayOfWeek" formula="DATEPART(dw, JoinDate) - 1" type="System.Int32" />
   <property name="FullName" formula="FirstName + ' ' + LastName" type="System.String" />
   <property name="JoinDate" type="System.DateTime">
     <column name="JoinDate" />
   </property>
   <property name="FirstName" type="System.String">
     <column name="FirstName" />
   </property>
   <property name="LastName" type="System.String">
     <column name="LastName" />
   </property>
 </class>
</hibernate-mapping>

var list = session.Query<User>.ToList();
foreach (var item in list)
{
   Console.WriteLine("{0}:{1}", item.FullName, item.DayOfWeek);
}

select
       user0_.UserId as UserId0_,
       user0_.JoinDate as JoinDate0_,
       user0_.FirstName as FirstName0_,
       user0_.LastName as LastName0_,
       DATEPART(user0_.dw, user0_.JoinDate) - 1 as formula0_, --- همان فرمول تعریف شده است
       user0_.FirstName + ' ' + user0_.LastName as formula1_ ---از طریق فرمول تعریف شده حاصل گردیده است
   from
       Users user0_