vb.net - Enumerate all controls in a form (redundant) -

i'm trying enumerate controls in form satisfy condition code beelow

public enum methodseachenum     startswith = 1     endswith = 2     contains = 3 end enum  public function getallcontrols(control control, key string, methodseach methodseachenum, controltype type, optional usetag boolean = true) ienumerable(of control)     dim controls = control.controls.cast(of control)()      return (controls.selectmany(function(ctrl) getallcontrols(ctrl, metodo)).concat(controls).where(function(c)             select case methodseach                 case metodoseachenum.endswith                     if (usetag)                         return c.tag.tostring.toupper.endswith(key.toupper) , c.gettype() controltype                      else                         return c.name.toupper.endswith(key.toupper) , c.gettype() controltype                      end if                 case metodoseachenum.startswith                     if (usetag)                         return c.tag.tostring.toupper.startswith(key.toupper) , c.gettype() controltype                      else                         return c.name.toupper.startswith(key.toupper) , c.gettype() controltype                      end if                 case metodoseachenum.contains                     if (usetag)                         return c.tag.tostring.toupper.contains(key.toupper) , c.gettype() controltype                      else                         return c.name.toupper.contains(key.toupper) , c.gettype() controltype                      end if                 case else                     return false             end select         end function)) end function 

inside form there groupbox , inside textbox. these textbox not returned , i'm not understanding why...

here how call function

dim ctrls = getallcontrols(formtagliente, "txtquote", metodoseachenum.startswith, gettype(textbox), false)          each txt textbox in ctrls               ...          next 

there imho few information answer question "why doesn't work specific case"
getallcontrols 2 argument missing in code maybe problem lies there
anyway toyed little code (but haven't tested it's more poc) , here's got :

enum searchmethod     startswith = 1     endswith = 2     contains = 3 end enum  function getallcontrols(of t control)(ctrl control, key string, method searchmethod, optional usetag boolean = true) ienumerable(of t)     ' todo validate args     dim upperkey = key.toupper      dim searchpredicates() func(of string, boolean) = {         function(src, tgt) src.startswith(upperkey),         function(src, tgt) src.endswith(upperkey),         function(src, tgt) src.contains(upperkey)     }     dim ctrlselector func(of control, string) = if(usetag, function(c) c.tag.tostring.toupper, function(c) c.name.toupper)      return getallcontrolsiterator(of t)(ctrl, ctrlselector, searchpredicates(cint(method) - 1)) end function  private iterator function getallcontrolsiterator(of t control)(ctrl control, ctrlselector func(of control, string), searchpredicate func(of string, boolean)) ienumerable(of t)     each child in ctrl.controls         if searchpredicate(ctrlselector(child)) andalso typeof child t yield directcast(child, t)          each grandchild in getallcontrolsiterator(of t)(child, ctrlselector, searchpredicate)             yield directcast(grandchild, t)         next     next end function 

the idea separate "construct criteria logic" actual "loop, search, yield" one, using generic constraint force targettype control (and having directly "good" return type). find simpler use iterator block that's more personal
maybe solve problem ?