How to detect picturebox drag drop on a line?

Someone can correct me if I'm wrong, but it's going to be complicated, I think.

First, I assume you're using the LineShape from within the Visual Basic PowerPacks? (and yes, I know this is a C# ?)

Even if you're not and just drawing a line on the form programmatically, you're going to have to use either the form's drag events, or the container that it is drawn on.

Assuming you already have a PictureBox being dragged, first hook the Form's DragEnter and DragOver events and in that code, first, check if there is a PictureBox present

if (e.Data.GetDataPresent(typeof(PictureBox))

then you have to check if it's over the line. If it's a LineShape from the VB PowerPacks, you can do a HitTest

if (lineShape1.HitTest(e.x,e.y))

Then, you set e.Effect to what effect you want. Then, you handle the DragDrop in the form and add the PictureBox to the line that the DragDrop happened over.