wpf - Listbox using a data template and dynamic data loading based on selection Enumeration Error -

to can or show me better way. have tried observable collection, list based on custom class, global/non-global collections, using listbox's itemssource, synclocking, , emptying , manually entering in items.

it tends work fine, every once in while error "collection modified; enumeration operation may not execute." seems occur @ system.collections.arraylist.arraylistenumeratorsimple.movenext()

i have tried few different things on past couple of weeks , able avoid sometimes, can reproduce in different area.

essentially, have 3 listboxes parent, current, children. these have captioned images in them. when image selected images in parent, current, , children empty , reload based on selected image.

i've written in vb, can convert c# if help. code has been changed many times , latest 1 has lot of commented code in it. or suggestions appreciated. simplify it, work, or performance enhancements great.

imagine code in triplicate. code identical exception of names.

<page.resources>      <collectionviewsource           source="{binding source={x:static application.current}, path=currentlist}"              x:key="currentlist" />  </page.resources>  <scrollviewer grid.row="2" verticalscrollbarvisibility="disabled"    panningmode="verticalonly" flowdirection="righttoleft" horizontalscrollbarvisibility="auto"                   >                 <listbox name="currentlistbox" verticalalignment ="stretch" margin=" 8" background="transparent"                            height="auto"   borderthickness="0" horizontalcontentalignment="center" flowdirection="lefttoright" horizontalalignment="center"                          itemssource="{binding currentlist}">                     <listbox.resources>                         <style targettype="{x:type listboxitem}">                             <eventsetter event="listboxitem.selected" handler="currentlistboxitem_selected" handledeventstoo="false"/>                 </style>                         </listbox.resources>                     <listbox.itemspanel>                 <itemspaneltemplate>                     <wrappanel isitemshost="true" />                 </itemspaneltemplate>                         </listbox.itemspanel>                     <listbox.itemtemplate>                 <datatemplate>                     <border borderbrush="#ff0000ac" style="{staticresource resourcekey=thumbnailborder}">                         <!--<viewbox maxwidth ="100" >-->                         <stackpanel>                              <grid>                                 <border  name="itemborder" style="{staticresource resourcekey=thumbnailinnerborder}"/>                                 <image name="personimage" maxheight ="200" maxwidth ="200" source="{binding profileimagepath}"                                                    horizontalalignment="center" >                                     <image.opacitymask>                                         <visualbrush visual="{binding elementname=itemborder}"/>                                     </image.opacitymask>                                 </image>                             </grid>                             <viewbox maxwidth ="190" margin="5,0,5,0" maxheight="15">                                 <textblock name="person" text="{binding profilename}" tag="{binding userid}" horizontalalignment="center" />                             </viewbox>                         </stackpanel>                         <!--</viewbox>-->                     </border>                 </datatemplate>                         </listbox.itemtemplate>                      </listbox>      </scrollviewer> 

the collection stored in global variable , populated using sqlce command.

public shared currentpeoplelist new collectionviewsource public shared current_people_list new observablecollection(of currents)()  public shared property currentlist() observablecollection(of currents)             return current_people_list     end     set(byval value observablecollection(of currents))         current_people_list = value      end set end property 

the custom class of currents:

public class currents implements inotifypropertychanged  private profilenamevalue string  private useridvalue integer  private profileimagepathvalue string  public event propertychanged propertychangedeventhandler implements inotifypropertychanged.propertychanged 

#region "properties getters , setters" public property profilename() string return me.profilenamevalue end set(byval value string) me.profilenamevalue = value onpropertychanged("profilename") end set end property

public property userid() integer             return me.useridvalue     end     set(byval value integer)         if value < 0             throw new argumentexception("user id must greater 0 ")         end if         me.useridvalue = value         onpropertychanged("userid")     end set end property  public property profileimagepath() string             return me.profileimagepathvalue     end     set(byval value string)         me.profileimagepathvalue = relativeprogrampath() & "media\pictures\" & value         onpropertychanged("profileimagepath")     end set end property   #end region  public sub new(byval userid integer, byval profilename string, byval profileimagepath string)     me.profilenamevalue = profilename     me.useridvalue = userid     me.profileimagepathvalue = if(profileimagepath "pack://*", profileimagepath, relativeprogrampath() & "media\pictures\" & profileimagepath)  end sub  protected sub onpropertychanged(byval name string)     raiseevent propertychanged(me, new propertychangedeventargs(name)) end sub  end class 

finally, way these populated using common function

 private sub reload(byval currentid integer)         try           try             parentlist = nothing             currentlist = nothing             childrenlist = nothing         catch         end try         try             me.parentlistbox.itemssource = nothing             me.currentlistbox.itemssource = nothing             me.childlistbox.itemssource = nothing         catch         end try         try              currentpersonid = currentid             'load images based on people.             dim ch = load_children_people(currentid)             dim c = load_current_people(currentid)             dim p = load_parent_people(currentid)              parentlist = if(p.count > 0, p, nothing)             currentlist = if(c.count > 0, c, nothing)             childrenlist = if(ch.count > 0, ch, nothing)         catch         end try         try              if parentlist isnot nothing _                 me.parentlistbox.itemssource = collectionviewsource.getdefaultview(parentlist)              if currentlist isnot nothing _                 me.currentlistbox.itemssource = collectionviewsource.getdefaultview(currentlist)             if childrenlist isnot nothing _                 me.childlistbox.itemssource = collectionviewsource.getdefaultview(childrenlist)         catch         end try        catch     end try     'for reason not work without pause. not sure why.     'fixme remove pause delay when able.      'thread.sleep(200) end sub 

i used lot of try-catch's attempt catch error, have been unsuccessful far. suspicion error occurs during ui thread cannot seem pin down. mentioned earlier. assistance great.