using System.Collections;

namespace TestModel
{
   public class DynamicEntity
   {
       public virtual int Id { get; set; }
       public virtual IDictionary Attributes { set; get; }
   }
}

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

namespace TestModel
{
   public class DynamicEntityMapping : IAutoMappingOverride<DynamicEntity>
   {
       public void Override(AutoMapping<DynamicEntity> mapping)
       {
           mapping.Table("tblDynamicEntity");
           mapping.Id(x => x.Id);
           mapping.IgnoreProperty(x => x.Attributes);
           mapping.DynamicComponent(x => x.Attributes,
                    c =>
                    {                        
                        c.Map(x => (string)x["field1"]);
                        c.Map(x => (string)x["field2"]).Length(300);
                        c.Map(x => (int)x["field3"]);
                        c.Map(x => (double)x["field4"]);
                    });
       }
   }
}

   drop table tblDynamicEntity

   create table tblDynamicEntity (
       Id INT IDENTITY NOT NULL,
      field1 NVARCHAR(255) null,
      field2 NVARCHAR(300) null,
      field3 INT null,
      field4 FLOAT null,
      primary key (Id)
   )

//insert
object savedId = 0;
using (var session = sessionFactory.OpenSession())
{
    using (var tx = session.BeginTransaction())
    {
        var obj = new DynamicEntity();
        obj.Attributes = new Hashtable();
        obj.Attributes["field1"] = "test1";
        obj.Attributes["field2"] = "test2";
        obj.Attributes["field3"] = 1;
        obj.Attributes["field4"] = 1.1;

        savedId = session.Save(obj);
        tx.Commit();
      }
}

INSERT
   INTO
       tblDynamicEntity
       (field1, field2, field3, field4)
   VALUES
       (@p0, @p1, @p2, @p3);
   @p0 = 'test1' [Type: String (0)], @p1 = 'test2' [Type: String (0)], @p2 = 1
[Type: Int32 (0)], @p3 = 1.1 [Type: Double (0)]

//query
using (var session = sessionFactory.OpenSession())
{
     using (var tx = session.BeginTransaction())
     {
         //using HQL
            var list = session
                          .CreateQuery("from DynamicEntity d where d.Attributes.field1=:p0")
                           .SetString("p0", "test1")
                           .List<DynamicEntity>();

              if (list != null && list.Any())
              {
                   Console.WriteLine(list[0].Attributes["field2"]);
              }
              tx.Commit();
       }
}

    select
       dynamicent0_.Id as Id1_,
       dynamicent0_.field1 as field2_1_,
       dynamicent0_.field2 as field3_1_,
       dynamicent0_.field3 as field4_1_,
       dynamicent0_.field4 as field5_1_
   from
       tblDynamicEntity dynamicent0_
   where
       dynamicent0_.field1=@p0;
   @p0 = 'test1' [Type: String (0)]

//update
using (var session = sessionFactory.OpenSession())
{
     using (var tx = session.BeginTransaction())
     {
           var entity = session.Get<DynamicEntity>(savedId);
           if (entity != null)
           {
                entity.Attributes["field2"] = "new-val";
                tx.Commit(); // Persist modification
            }
       }
}

//delete
using (var session = sessionFactory.OpenSession())
{
    using (var tx = session.BeginTransaction())
    {
         var entity = session.Get<DynamicEntity>(savedId);
         if (entity != null)
         {
              session.Delete(entity);
              tx.Commit();
          }
     }
}