Why when I use method Compare from format dxf result in pdf?

[altamir95]

My code:

using (Comparer comparer = new Comparer("source.dxf"))
{
    comparer.Add("target.dxf");
    comparer.Compare("result.dxf");
}

And after that I can see in directory file "result.pdf", not "result.dxf". Please, I need to your help, thank you.