Hi NNT,

Unfortunately SymbolElement's SymbolSize isn't a dependency property, but as a workaround you can create a new dependency property that dispatch every change to the map element's one. E.g.:

In XAML:

 <igMap:XamMap x:Name="xamMap1">
 <igMap:XamMap.Layers>
  <igMap:MapLayer x:Name="MapLayer" IsAutoWorldRect="True" >
   <igMap:MapLayer.Reader>
    <igMap:ShapeFileReader Uri="Shapefiles/usa/usa_st" DataMapping="Name,Caption=STATE_NAME"/>
   </igMap:MapLayer.Reader>             
  </igMap:MapLayer>
  <igMap:MapLayer x:Name="symbolLayer">   
  </igMap:MapLayer>
 </igMap:XamMap.Layers>
</igMap:XamMap>

In Code behind

1. The SymbolSize Dependency property

#region SymbolSize

public double SymbolSize
{
 get { return (double)GetValue(SymbolSizeProperty); }
 set { SetValue(SymbolSizeProperty, value); }
}

public static readonly DependencyProperty SymbolSizeProperty =
 DependencyProperty.Register("SymbolSize", typeof(double), typeof(ButtonSymbol),
 new PropertyMetadata(0.0, OnSymbolSizeChanged));

private static void OnSymbolSizeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
 ((ButtonSymbol)d).OnSymbolSizeChanged((double)e.OldValue, (double)e.NewValue);
}

private void OnSymbolSizeChanged(double oldValue, double newValue)
{
 ((SymbolElement) xamMap1.Layers[1].Elements[0]).SymbolSize = newValue;
}

#endregion 

2. Create a SymbolElement at specific coordinates

var element = xamMap1.Layers[0].Elements.FindElement("Name", "Montana").ElementAt(0);

var origin = new Point(element.WorldRect.X + 0.5 * element.WorldRect.Width, element.WorldRect.Y + 0.5 * element.WorldRect.Height);
var symbolElement = new SymbolElement { SymbolOrigin = origin, SymbolType = MapSymbolType.Diamond, SymbolSize = 10 };

xamMap1.Layers[1].Elements.Add(symbolElement);

Rect worldRect = xamMap1.Layers[1].WorldRect;
worldRect.Union(symbolElement.WorldRect);
xamMap1.Layers[1].WorldRect = worldRect; 

3. Animate custom SymbolSize DP that changes to the SymbolElement's SymbolSize:

var sb = new Storyboard();

var animation = new DoubleAnimation();
animation.To = 20;
animation.Duration = TimeSpan.FromSeconds(2.0);
animation.RepeatBehavior = RepeatBehavior.Forever;

Storyboard.SetTarget(animation, this);
Storyboard.SetTargetProperty(animation, new PropertyPath(SymbolSizeProperty));
sb.Children.Add(animation);
sb.Begin(); 

Please let me knof if that works for you.

Regards,

Ivan Kotev