Dapper try to find Int32 parameters construtor when query returns no row

Hi,

I have this SQL query

SELECT 
t.Id, t.Name, t.Epoch, t.RightAscension, t.Declination, 
s.TargetId, s.Id, s.FilterIndex, s.Binning, s.Duration, s.Number, s.Completed
FROM Targets t 
LEFT OUTER JOIN Sequences s ON s.TargetId = t.Id"

that I execute with :

using (IDbConnection connection = _dbConnectionFactory.OpenConnection())
{
    var targets = new Dictionary<int, Target>();
	
    return connection.Query<Target, Sequence, Target>(
        sql, (target, sequence) =>
        {
            if (!targets.TryGetValue(target.Id, out Target targetEntry))
            {
                targetEntry = target;
                targets.Add(targetEntry.Id, targetEntry);
            }

            if (sequence != null)
            {
                targetEntry.AddSequence(sequence);
            }

            return targetEntry;
        },
        splitOn: "TargetId").Distinct();
}

As some values are related to a complex object I have this constructor and no parameterless constructor :

private Target(long id, string name, long epoch, double rightAscension, double declination)
{
    Id = id;
    Name = name;
    Coordinates = new Coordinates(rightAscension, declination, epoch);
    Sequences = new List<Sequence>();
}

It works perfectly, except if the query doesn't return any row. In this case I get this error :

A parameterless default constructor or one matching signature (System.Int32 Id, System.Int32 Name, System.Int32 Epoch, System.Int32 RightAscension, System.Int32 Declination) is required.

Why does it try to find a constructor that does not match the types of the table. And why does it try to find a constructor that will never be called (the request does not returns any row) ?

As a workaround I added a constructor that looks like :

private Target(int id, int name, int epoch, int rightAscension, int declination)
{
	throw new InvalidOperationException($"This constructor should not have been called (parameters : id={id}, name={name}, epoch={epoch}, rightAscension={rightAscension}, declination={declination}");
}

Regards,

Julien

Reproduce the issue through connection.Query<Target, Sequence, Target> using the shown SQL and Target constructor, comparing an empty result with a result containing rows. Trace the constructor-selection path for Target and determine why the signature reports Int32 parameters; done means the behavior is explained and the unexpected empty-result handling is corrected or covered.