The connection is already in a transaction and cannot participate in another transaction - ef-core-2.1

Question

I am calling this method:
public IEnumerable<T> ExecuteObject<T>(string query, Func<DbDataReader, T> map)
{
var trx = miContexto.Database.BeginTransaction();
var entities = new List<T>();
miContexto.Database.OpenConnection();
using (var command = miContexto.Database.GetDbConnection().CreateCommand())
{
command.CommandText = query;
command.CommandType = CommandType.Text;
command.Transaction = trx.GetDbTransaction();
using (var result = command.ExecuteReader())
{
while (result.Read())
{
entities.Add(map(result));
}
}
}
trx.Commit();
trx.Dispose();
return entities;
}
From MVC controller by this lines:
var result = c.ExecuteObject(
"SELECT TOP 10 Nombre, Apellido FROM Persona "
+ " GROUP BY Nombre, Apellido ORDER BY Apellido DESC",
x => new Persona {
Nombre = (string)x[0],
Apellido = (string)x[1], });
result.ToList();
return View();
It works most of the time but every often it throws the exception "The connection is already in a transaction and cannot participate in another transaction".
Any ideas. I tried to solve it in many different ways but unsuccessfully.
I used using(transaction scope), using(dbcontext.database.opentransaction). but this exceptions appears with all this options.