Silverlight Combobox - Setting the SelectedItem MVVM -

i have viewmodel sets value "userstructure" property. problem combobox wont bind value.

public class owneroccupieraccountviewmodel : viewmodelbase {     /// <summary>     /// load combobox structures     /// </summary>     private readonly loadoperation<structure> _loadstructures;      private readonly loadoperation<unitoccupierdetail> _loadunitoccupierdetails;      //public icommand saveaccountsettingscommand { get; set; }      #region properties      private observablecollection<structure> _structures;     public observablecollection<structure> structures     {         { return _structures; }          set         {             _structures = value;             raisepropertychanged("structures");         }     }      private structure _userstructure;     public structure userstructure     {         { return _userstructure; }         set         {             _userstructure = value;             raisepropertychanged("selectedstructure");         }     }      private unitoccupierdetail _unitoccupierdetail;     public unitoccupierdetail unitoccupierdetail     {         { return _unitoccupierdetail; }         set         {             _unitoccupierdetail = value;             raisepropertychanged("unitoccupierdetail");         }     }       #endregion      public owneroccupieraccountviewmodel()     {         // saveaccountsettingscommand = new delegatecommand(saveaccountsettings, cansave);          useraccountcontext _useraccountcontext;          if (!designerproperties.isindesigntool)         {             var loggedinuser = new guid(webcontext.current.user.userid.tostring());              _useraccountcontext = new useraccountcontext();              #region load structures             _loadstructures = _useraccountcontext.load(_useraccountcontext.getstructuresquery());             _loadstructures.completed += _loadstructurescompleted;             #endregion              #region load user data              _loadunitoccupierdetails =                 _useraccountcontext.load(                     _useraccountcontext.getunitoccupierdetailsquery().where(                         u => u.useridfk == loggedinuser && u.structurefk == 92));             _loadunitoccupierdetails.completed += _loadunitoccupierdetails_completed;             #endregion         }     }      void _loadunitoccupierdetails_completed(object sender, eventargs e)     {         _unitoccupierdetail= new unitoccupierdetail();         _unitoccupierdetail = _loadunitoccupierdetails.entities.first();          _userstructure = _unitoccupierdetail.structure;     }      void _loadstructurescompleted(object sender, eventargs e)     {         var thesestructures = new observablecollection<structure>(_loadstructures.entities);         structures = thesestructures;     }      //private void saveaccountsettings(object param)     //{      //}      //private static bool cansave(object param)     //{     //    return true;     //} }   <combobox x:name="cboapartments"                            itemssource='{binding structures, mode=twoway}'                           displaymemberpath='structurename'                           selectedvaluepath='idstructure'                           selecteditem='{binding selectedstructure,mode=twoway}'                           width="200"                           height="25"> 

in xaml selecteditem bound selectedstructure instead of userstructure want

update:

your code doesn't work because should set selecteditem object has reference equality object in itemssource. in viewmodel set structures result of 1 service operation , userstructure result of other. userstructure , object in structures can equals (object.equals) not reference equals (object.referenceequals). combobox other itemscontrols doesn't compare items equality, compares identity. so, have right code should select structures object equals userstructure , set userstructure:

   void _loadunitoccupierdetails_completed(object sender, eventargs e)    {         ...          structure userstructure = structures.firstordefault(s=>s.equals(_unitoccupierdetail.structure));         userstructure = userstructure;    } 

in case should sure structures comes before. can @ reactive extensions observable.forkjoin() method syncronize 2 async calls.