WingDing fonts for TextSymbol

[BinGan]

I am trying to add TextSymbol on map with WingDing fonts and the map is displaying the unicode directly.

My codes are as follows,

var displayString:String = "■";
var textFormat:TextFormat = new TextFormat("WingDing");
textFormat.color = 0x00FF00;
markerSymbol = new TextSymbol(displayString,null,color);
(markerSymbol as TextSymbol).textFormat = textFormat;
marker = new Graphic(markerPoint,markerSymbol,attributes);
_markerLayer.add(marker);