How can I set the rotation angle field for the icon I used in an streamlayer?

I use a workflow to change the renderer of my StreamLayer.

This is the current Renderer: New ESRI.ArcGIS.Client.SimpleRenderer() With { .Symbol = new ESRI.ArcGIS.Client.Symbols.PictureMarkerSymbol() With { .Source = new System.Windows.Media.Imaging.BitmapImage(new Uri(URL_to_the_symbol, UriKind.Absolute)),.OffsetY=0,.OffsetX=0}}

The streamlayer has a field with the rotation angle, how can I set it?

Thanks!