MSSQL Legacy Data Types in NHibernate.Mapping.ByCode.Conformist

Trying to migrate the code generation of NHibernate data classes and mappings from 2.1.2 to 3.2 and from Fluent to Mapping ByCode Conformist, I noticed a couple of problems relating mostly to non-Unicode string fields and legacy data types such as image and ntext.

Typically, column mapping uses the Property() method for columns like to NVARCHAR column:

public partial class Application_Map: ClassMapping<Application>
{
  public Application_Map()
  {
    Property(x => x.ID, map =>
      {
        map.Column("ID");
        map.NotNullable(true);
        map.Length(100);
      });
  }
}

This kind of declaration raised a HibernateException for VARCHAR columns  in configuration.BuildSessionFactory()

Wrong column type in MyDatabase.dbo.Foo for column Bar. Found: varchar, Expected NVARCHAR(256)

To fix this exception, the varchar column needs to be declared like this:

  Property(x => x.VarcharFoo, map =>
    {
      map.Column(c =>
        {
          c.Name("VarcharFoo");
          c.SqlType("varchar");
          c.Length(50);
        });
    });

Similarly, we can declare the native SQL data type for image and ntext columns:

  Property(x => x.FooImage, map =>
    {
      map.Column(c =>
        {
          c.Name("FooImage");
          c.SqlType("image");
        });
      map.Lazy(true);
    });
  Property(x => x.FooNText, map =>
    {
      map.Column(c =>
        {
          c.Name("FooNText");
          c.SqlType("ntext");
        });
    });