Get a list of mapped data in Nhibernate

Question

I am trying to transform the data returned from the database to the settings made in my mapping, however I get the following criticism:

"The value "System.Object[]" is not "Domain.Classes.Classeemplo" and cannot be used in this generic collection."

I’ve tried using the "Transformers.Aliastoben", however I realized that ignores all my mapping. I am still very new in this area, if anyone can help me I thank you.

My Class:

public class ClasseExemplo
{
    public virtual int ID { get; set; }
    public virtual string Descricao { get; set; }
    public virtual Usuario Usuario { get; set; }
    public virtual DateTime TimeStamp { get; set; }
}

Mapping:

    public ClasseExemploMap()
    {
        Id(x => x.ID);
        Map(x => x.Descricao);
        Refereces(x => x.Usuario).Column("USUARIO_ID").Cascade.None();
        Map(x => x.TimeStamp);

        Table("TABELA");
    }

Repository:

public IList<ClasseExemplo> BuscarLista(int usuario)
{
    string SQL = "select * " +
     "from MinhaTabela " +
     "where Usuario_ID = :id";

    return Session.CreateSQLQuery(SQL)
           .SetParameter("id", usuario)
           //.SetResultTransformer(Transformers.AliasToBen(typeof(ClasseExemplo))
           .List<ClasseExemplo>();
}

Answer 1

Yes, I ended up doing a test and it works perfectly, I think it’s doing something wrong, an example to illustrate:

Class

public class Credit
{
    public virtual int Id { get; set; }
    public virtual string Description { get; set; }
    public virtual DateTime? Created { get; set; }
}

Mapclass

public class CreditMap: ClassMap<Credit>
{
    public CreditMap()
    {
        Table("credit");

        Id(x => x.Id)
            .Column("id")
            .GeneratedBy.Sequence("credit_id_seq");

        Map(x => x.Description)
            .Column("description")
            .Length(100)
            .Not.Nullable();

        Map(x => x.Created)
            .Column("created")
            .Nullable();
    }
}

Now to search a id that will bring only one item:

int id = 1;
var creditFindId = connection
            .CreateSqlQuery("SELECT * FROM credit WHERE id=:id")            
            .SetResultTransformer(Transformers.AliasToBean<Credit>())
            .SetParameter("id", id)
            .UniqueResult<Credit>(); // Resultado único

or to filter by a specific field to bring an item list:

int id = 1;
var creditFindId = connection
    .CreateSqlQuery("SELECT * FROM credit WHERE id=:id")
    .SetResultTransformer(Transformers.AliasToBean<Credit>())
    .SetParameter("id", id)
    .List<Credit>(); // Lista

because that kind of method of NHibernate return the data in a object array (object[]) and not in a strongly typed type, for that you need to use:

• .SetResultTransformer(Transformers.AliasToBean<Credit>()) to know what kind of data should be processed
• .UniqueResult<Credit>() or .List<Credit>() for the specific type forcing the previous configuration.

If it is to make filters and already treat the data with the specific type without using SQL can be done as well:

int id = 1;
var item1 = connection.QueryOver<Credit>()
     .And(x => x.Id == id) // filtro
     .SingleOrDefault<Credit>(); // Resultado único

---

int id = 1;
var list1 = connection.QueryOver<Credit>()
     .And(x => x.Id == id) // filtro
     .List<Credit>(); // Lista

^{Observing: where it is written //filtro can be placed other as many filters and ordering.}

Remember that if the result is by the primary key you can do so:

int id = 1;
Credit credit = session.Get<Credit>(id);

and so on, it’s not too difficult once you take the methods and their functionality is quiet handling.