void SmartPieChart_OnOnPieceMouseLeave(object sender, SmartPieChartPieceMouseEventArgs e)
 {
     ViewModel.MouseLeavePiece();
 }
 void SmartPieChart_OnOnPieceMouseEnter(object sender, SmartPieChartPieceMouseEventArgs e)
 {
     ViewModel.MouseEnterPiece(e.Label);
 }