c# - Two Reordering ListBoxes on Same page, prevent user from dragging and dropping between -

i have wpf c# application has window 2 reordering listboxes right next each other. used examples in this link make listbox user control. unfortunately allows user drag 1 box , drop in other. how can make sure doesn't happen?

here code:

    public void setitems(list<string> values){         _items = new observablecollection<item>();         foreach (string s in values)         {             _items.add(new item(s));         }          listbox.displaymemberpath = "name";         listbox.itemssource = _items;          listbox.previewmousemove += listbox_previewmousemove;          var style = new style(typeof(listboxitem));         style.setters.add(new setter(listboxitem.allowdropproperty, true));         style.setters.add(             new eventsetter(                 listboxitem.previewmouseleftbuttondownevent,                 new mousebuttoneventhandler(listboxitem_previewmouseleftbuttondown)));         style.setters.add(                 new eventsetter(                     listboxitem.dropevent,                     new drageventhandler(listboxitem_drop)));         listbox.itemcontainerstyle = style;     }       private void listbox_previewmousemove(object sender, mouseeventargs e)     {              point point = e.getposition(null);             vector diff = _dragstartpoint - point;             if (e.leftbutton == mousebuttonstate.pressed &&                 (math.abs(diff.x) > systemparameters.minimumhorizontaldragdistance ||                     math.abs(diff.y) > systemparameters.minimumverticaldragdistance))             {                 var lb = sender listbox;                 var lbi = findvisualparent<listboxitem>(((dependencyobject)e.originalsource));                 if (lbi != null)                 {                     dragdrop.dodragdrop(lbi, lbi.datacontext, dragdropeffects.move);                 }             }      }       private void listboxitem_previewmouseleftbuttondown(object sender, mousebuttoneventargs e)     {         _dragstartpoint = e.getposition(null);     }       private void listboxitem_drop(object sender, drageventargs e)     {         if (sender listboxitem)         {             var source = e.data.getdata(typeof(item)) item;             var target = ((listboxitem)(sender)).datacontext item;                   int sourceindex = listbox.items.indexof(source);                 int targetindex = listbox.items.indexof(target);                  debug.writeline("target: " + targetindex.tostring());                  move(source, sourceindex, targetindex);          }     }       private void move(item source, int sourceindex, int targetindex)     {         if (sourceindex < targetindex)         {             _items.insert(targetindex + 1, source);             _items.removeat(sourceindex);         }         else         {             int removeindex = sourceindex + 1;             if (_items.count + 1 > removeindex)             {                 _items.insert(targetindex, source);                 _items.removeat(removeindex);             }         }     } } 

i figured out in case else has similar issue...

i changed move function following:

 private void move(item source, int sourceindex, int targetindex)         {             ilist<item> previtems = _items;              try             {                 _items.removeat(sourceindex);                 _items.insert(targetindex, source);              }             catch(argumentoutofrangeexception)             {                 //user doesn't need notified this. means dragged out of box ordering.                  //the application not need stopped when happens.                 _items = previtems;                 debug.writeline("user tried drag between boxes.. order of boxes not changed. ");              }         } 

i realized if remove item first won't have worry changing target or remove index based on position of sourceindex in relation targetindex. instead can wrap in try catch , argumentoutofrangeexception, happen if user tries drag , drop between. if happens reset box previous items.

as far can tell solution works fine... there may have been simpler way go this.