Some value return null on Dapper Multi Mapping

Question

I'm having a problem using Dapper. I have a list of the Rubrica class that contains the field valore. When I run a query with a JOIN and identify the agenda type, the valore field remains set to null

My two classes Rubrica and TipoAgenda

public class Rubrica // Same as table anagrafico_rubrica
{
    public int id_rubrica { get; set; }
    public string cod_anagrafica { get; set; }
    public string descrizione_contatto { get; set; }
    public TipoRubrica tipo { get; set; }
    public string valore { get; set; }
}

public class TipoRubrica // Same as table anagrafico_tipo_rubrica
{
    public int id_tipo_rubrica { get; set; }
    public string descrizione_tipo_rubrica { get; set; }
}

I created a function that returns me a list of Agenda doing a JOIN with table anagrafico_tipo_rubrica

    public List<Rubrica> GetAgendaAnagrafico(string codiceAnagrafico)
    {
        using (DatabaseConnection db = new DatabaseConnection())
        {
            const string query = @"SELECT * FROM anagrafico_rubrica JOIN anagrafico_tipo_rubrica ON tipo = id_tipo_rubrica WHERE cod_anagrafica = @anagrafico";
            var parametri = new { anagrafico = codiceAnagrafico };
            return db.con.Query<Rubrica, TipoRubrica, Rubrica>(query, (rubrica, tipo) => { rubrica.tipo = tipo; return rubrica; }, parametri, splitOn: "tipo").ToList();
        }
    }

Here you can see what the query returns

And here you see how int the Agenda list there is the value of valore set to null

score 7 · Accepted Answer · answered Apr 21 '16 at 08:16

7

You are splitting on tipo, which comes before valore in your query, so dapper is splitting the columns and thinking valore is for TipoRubrica instead of for Rubrica

Select the order of the fields explictly on your query

SELECT id_rubrica, 
       cod_anagrafica, 
       descrizione_contatto, 
       valore, 
       tipo,       // <-- you are splitting here. columns above are for 
                   //     first type, columns below for second
       id_tipo_rubrica, 
       descrizione_tipo_rubrica 
    FROM ...

So when you split on tipo, valore is before that, and it's mapped to the first type (Rubrica), instead of to the second (TipoRubrica)

answered Apr 21 '16 at 08:16

Jcl

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Tried it, it works! I thought Dapper could understand which field automatically associate the values considering the name of the class. – Lorenzo Belfanti Apr 21 '16 at 08:19
1

By convention, it splits on `Id` fields, but if you are specifically telling it on which column to split on (on the parameter `splitOn: "tipo"`), it'll do as you command it to ;-) – Jcl Apr 21 '16 at 08:20
Even if it was not the case, it's wise to (unless you have a very specific need not to) choose the fields you need on your queries explicitly, and not use `SELECT *` :-) – Jcl Apr 21 '16 at 08:22
Yes, usually i select only the fields that interest me, but in this case they were all – Lorenzo Belfanti Apr 21 '16 at 08:24

Some value return null on Dapper Multi Mapping

1 Answers1