Read Mulitiple selected item of List Box Using Flex

How to read multiple selection list box in flex?

<mx:List allowMultipleSelection="true"
id="searchResult" width="100%"
height="100"
verticalScrollPolicy="on"
click="filter">

<mx:dataProvider>
<mx:Object label="Schmidt, Frank" value="1"/>
<mx:Object label="Schmidt, Peter" value="2"/>
</mx:dataProvider>
</mx:List>


function filter():void{
var str:String="";
for each(var ob:Object in searchResult.selectedItems){
str+=(str=="")?ob.value.toString():","+ob.value.toString();
i++;
}
trace(str); // this will return you indexs of list box
}