asp.net - Unable to debug web control click handler -

asp.net webforms application. there custom web control (ie inherits system.web.ui.webcontrols.webcontrol). can put breakpoints anywhere in createchildcontrols() or other overloaded method , these breakpoints work fine. however, if try add breakpoint method bound button on page, error on breakpoint:

the breakpoint not hit.  no executable code of debugger's target code associated line.  possible causes include: conditional compilation, compiler optimizations, or target architecture of line not supported current debugger code type. 

i've tried cleaning solution, deleting bin/obj folders, restarting local iis, recycling app pool, no avail.

code in vb.net (sorry). here function definition (in webcontrol code):

 private sub addtocartclick(byval sender object, byval e system.eventargs)       // breakpoint on line 1 

here code ties function button:

 dim button = new button  addhandler button.click, addressof addtocartclick 

the code executes , has worked long time, cannot debug breakpoints.