Polyline disappears while setting PolylineStyle property of a line series in a Silverlight chart.

Question

I have a silverlight chart which has multiple line series that was dynamically created.

When I assign a PolylineStyle of the dynamically created LineSeries the lines in chart disappear. Only markers are shown. It is odd because when I assign the same style from xaml everything works as it should.

I'm using the following code to assign the style:

agentSeries.PolylineStyle = (Style)AgentsChart.Resources["AgentResultChartLineStyle"];

this style contains only one setter - StrokeThickness = 2.

Am I doing something wrong here? Why do the lines disappear when I set the PolylineStyle from code on the dynamically added LineSeries?