Take only the return value in a Dapper

Question

A query returns this?

var teste = _connection.Query(sQuery.ToString(), par).FirstOrDefault();

well, within the var test I have it:

UF = "MA"

but I just want the MA.

How do I make Dapper return me only the value?

Answer 1

In this case, Dapper should return an object of the type dynamic.

Just do it like this:

var teste = _connection.Query(sQuery.ToString(), par).FirstOrDefault().UF;

Like the guy dynamic is an implementation of Late Binding, it transfers the responsibility of knowing the content of the object to the programmer at runtime. This is usually a 'double vegetable knife'. At the same time that it gives this type of convenience, the code is fragile for maintenance and a small change in its variable sQuery, for example, can cause problems.

In this type of situation, you can mitigate the negative effects of using Dynamic by explaining what you expect as a return already in your query.

Suppose your query is like this:

string sQuery = "SELECT TOP 1 UF FROM TabelaCidade WHERE codigo = @Codigo";

You should be able to receive the same result - and in a less fragile way - if you do the Query that way:

var teste = _connection.Query<string>(sQuery.ToString(), par).FirstOrDefault();

Thus, you will know at compile time the variable type teste and is less susceptible to future errors.

Answer 2

With Dapper you have several ways to do this, below are examples:

//Aqui você está tipando o retorno em string e já pegando o primeiro resultado
var uf = _connection.QueryFirstOrDefault<string>(sQuery.ToString(), parm);

//Aqui você converte o retorno no seu model, e posteriormente poderá pegar seuModel.UF (onde uf é a propriedade)
var teste = _connection.Query<SeuModel>(sQuery.ToString(), par).FirstOrDefault();
var uf = teste.UF;

On the website http://dapper-tutorial.net/dapper you can find more information.