c# - MVVM light Silverlight multiple Selection list box initial selection on page load -

i using mvvm light , have list box multiple selection. in mainpage.xaml have

<listbox name="listbox1" itemssource="{binding items}" grid.column="1" horizontalalignment="stretch" verticalalignment="stretch" background="transparent"  margin="15,15,18,0" selectionmode="multiple" height="100" /> 

in mainpage.xaml.cs have (i not want use dependency property reason).

mainpage() {     listbox1.selectionchanged = new selectionchangedeventhandler(listbox1_selectionchanged); }  void listbox1_selectionchanged(object sender, selectionchangedeventargs e) {  var listbox = sender listbox;  var viewmodel = listbox.datacontext mainviewmodel;  viewmodel.selecteditems.clear();  foreach (string item in listbox.selecteditems)      viewmodel.selecteditems.add(item); } 

and works fine , binds mainviewmodel. when page loaded want first item of the collection items selected default. please let me know how implement this

i'd recommend using listbox's loaded event , bind first item in collection:

mainpage() {     listbox1.loaded += new routedeventhandler( onlistbox1loaded );     listbox1.selectionchanged += new selectionchangedeventhandler(listbox1_selectionchanged); }  private void onlistbox1loaded( object sender, routedeventargs e ) {     // make sure selection changed event doesn't fire     // when selection changes     listbox1.selectionchanged -= mylist_selectionchanged;      listbox1.selectedindex = 0;     e.handled = true;      // re-hook selection changed event.     listbox1.selectionchanged += mylist_selectionchanged; } 

edit

if can not use loaded event, you'll need create property in model hold item want selected , assign property selecteditem property of listbox.

public class mymodel : inotifypropertychanged {    private observablecollection<someobject> _items;   public observablecollection<someobject> items   {     { return _items; }     set     {         _items = value;         notifypropertychanged( "items" );     }   }    private someobject _selected;   public someobject  selected   {     { return _selected; }     set     {         _selected = value;         notifypropertychanged( "selected" );     }   }    public void somemethodthatpopulatesitems()   {     // create/populate items collection      selected = items[0];   }    // implementation of inotifypropertychanged excluded brevity  } 

xaml

<listbox itemssource="{binding path=items}"           selecteditem="{binding path=selected}"/> 

by having property holds selected item, have access in model item whenever selected item changed user.