private static void GiveNameToUnnamedLabels(IEnumerable<Line> finalCode)
{
    int count = 0;

    void GiveName(Model.Label label)
    {
        label.Name = $"dyn_label{++count}";
    }

    var unnamed = finalCode.Where(x => x.Label != null && x.Label.Name == null).ToList();
    unnamed.ForEach(x => GiveName(x.Label));
}

private static void NameUnnamedLabels(IEnumerable<Line> finalCode)
{
    int labelNo = 0;

    void GiveName(Model.Label label) => label.Name = $"dyn_label{++labelNo}";

    var unnamedLables = finalCode
        .Select(ln => ln.Label)
        .Where(lbl => lbl != null && lbl.Name == null);
    unnamedLables.ForEach(GiveName);
}