Hi Joska,
its a simple method to set simbolizer settings
to more opportunities see other properties and methods of LineSymbolizer..
I hope this help..
its a simple method to set simbolizer settings
LineSymbolizer plineSymb = new LineSymbolizer(true);
plineSymb.SetFillColor(Color.Red);
plineSymb.SetWidth(2.0d);
YourLineLayer.SelectionSymbolizer = plineSymb
to more opportunities see other properties and methods of LineSymbolizer..
I hope this help..