Datasources refreshing


I've loaded CZML files (containing polygons) into Cesium using Cesium.CzmlDataSource.load().
Then on one of the button click, I'm drawing border to those polygons. In console I see that their property is updated properly. But I do not see that effect on Viewer.
Sometimes it shows outline for particular polygon if I click on it. So its like it updates Viewer element on click.

Any suggestions on how to refresh the view?

Here is code to toggle outline.

Val = !Val;
var viewer_entities = viewer.dataSources.get(0).entities;
var item = "";
console.log("items : "+viewer_entities._entities._array.length);
for(var i=0;i<viewer_entities._entities._array.length;i++)
  item = viewer_entities._entities._array[i];
  if(item.polygon != undefined)
    item.polygon.outline._value = Val;

In your code sample you are manipulating private members (indicated by the underscore prefix). This bypasses all of the logic in those classes. Your code should not access or modify any private members with an underscore in their name. Use only the public API listed in the documentation.