Aforge ExtractBiggestBlob implementation for detect line

Question

I have an image treshold, i want to detect just a line in image and deleted the noise small black point. I do use aforge framework but its not work. the threshold from aforge from v.2.0 And I have problem with treshold to when aforge version change to v.2.2.5 I have a code like this

filter = new Bitmap(picCanvas.Image);
        mean = new Mean();
        threshold = new Threshold(162);
        filter = mean.Apply(filter);
        filter = threshold.Apply(filter);
        picCanvas.Image = filter;
        picCanvas.Refresh();

it can't work at aforge v.2.2.5

the question is

1. how to convert code v.2.0 to v.2.2.5 aforge framework
2. how implement ExtractBiggestBlob to get just a line in image thanks