Question

I’ve got a class called ‘MusicNote’ which inherits from ‘PictureBox’. I’m trying to make it drag vertically when the user clicks on it and moves the mouse up/down. I’ve pasted the code below, which works. The problem is that it only works the first time – i.e. the user drags it and it’s placed in the new position as it’s supposed to. However, when I click it again and drag – it disappears. Any ideas?

Answer 1

Problem is with the MouseUp event handler. In that event you will have to unsubscribe to MouseMove event handler.

    public void MusicNote_MouseUp(object sender, MouseEventArgs e)
    {
        isDragging = false;
        this.MouseMove -= new MouseEventHandler(OnDrag);
    }

Multiple subscription to same event is causing your controls top value to be negative.