xaml - WPF Pie chart doesn't slice up -

i using piechart control display 2 values database (used , available). output without slicing seen in image below,

how slice pie chart?

my keyvalue pair of type . getting values keyvaluepair datasource & retrieving using linq sql queries.

xaml pie chart:

 <window.resources>   <collectionviewsource x:key="ramview" source="{binding path=usagerams, source={staticresource serverview}}"/>  </window.resources>   <dvc:chart x:name="ram" background="white" foreground="black" margin="950,0,92,485" grid.column="1" grid.row="1">  <dvc:chart.series>  <dvc:pieseries itemssource="{binding}"  dependentvaluepath="available" independentvaluepath="used" >                                 </dvc:pieseries>  </dvc:chart.series> </dvc:chart> 

code behind

 private collectionviewsource serversusageramsviewsource;   private void window_loaded(object sender, routedeventargs e)     {     var ramlist = (from c in db.usagerams                   orderby c.usageramid descending, c.used,c.available,c.total                   select c).take(1);     this.serversusageramsviewsource  = (collectionviewsource)this.findresource("ramview");     serversusageramsviewsource.source = ramlist;    } 

well guess should have 2 series.

<dvc:chart ...>      <dvc:chart.series>           <dvc:pieseries itemssource="{binding}" dependentvaluepath="available" />           <dvc:pieseries itemssource="{binding}" dependentvaluepath="used" />      </dvc:chart.series> </dvc:chart>    

disclaimer - didn't test it, that's try.