windows store apps - XAML ComboBox default SelectedIndex is not shown -

i have combobox values, , want have 2 things working @ once.

here combobox , want show 10 default value , bind double? distance property.

<combobox grid.row="5" grid.column="1"           selectedindex="1"           selectedvalue="{binding distance, mode=twoway, converter={staticresource stringtodoubleconverter}}">     <comboboxitem>1</comboboxitem>     <comboboxitem isselected="true">10</comboboxitem>     <comboboxitem>100</comboboxitem>     <comboboxitem>1000</comboboxitem> </combobox> 

and here converter:

public class stringtodoubleconverter : ivalueconverter {     public object convert(object value, type targettype, object parameter, string language)     {         return null;     }      public object convertback(object value, type targettype, object parameter, string language)     {         comboboxitem item = value comboboxitem;          if (item != null)         {             double d;             if (double.tryparse(item.content.tostring(), out d))                 return d;         }          return null;     } } 

the problem in code, selected item 10 not show @ start of application. if remove line converter, show selected item 10, then, can't bind double? distance property. dont want write code behind it, such as: convert.todouble(combobox1.selectedvalue)...

what can make both things work?

you need populate combo box items viewmodel. should not use selectedvalue property, instead of should use selecteditem. see below given code.

xaml

<combobox x:name="cmb" itemssource="{binding distancecollection}"                      selecteditem="{binding distance, converter={staticresource stringtodoubleconverter}, mode=twoway}"/> 

viewmodel

public class viewmodel : inotifypropertychanged {     public viewmodel()     {         distancecollection = new observablecollection<string>          {             "1",             "10",             "100",             "1000"         };          distance = double.parse(distancecollection[1].tostring());     }      public observablecollection<string> distancecollection { get; set; }      private double _distance;     public double distance     {                  {              return _distance;          }         set         {             _distance = value;             onpropertychanged("distance");         }     }      public event propertychangedeventhandler propertychanged;      protected void onpropertychanged(string propertyname = null)     {         var eventhandler = this.propertychanged;         if (eventhandler != null)         {             eventhandler(this, new propertychangedeventargs(propertyname));         }     } } 

converter

public class stringtodoubleconverter : ivalueconverter {     public object convert(object value, type targettype, object parameter, string language)     {         return value.tostring();     }      public object convertback(object value, type targettype, object parameter, string language)     {         string item = value string;          if (!string.isnullorwhitespace(item))         {             double d;             if (double.tryparse(item, out d))                 return d;         }          return null;     } }