Polyline on Xamarin

Talissimo

Hello
I would like to be able to click are my polyline but nothing, I want to display information like a pin.

But my code does not give results ... do you have any idea ?

polyline.IsClickable = true;
polyline.Clicked += (sender, e) =>
{

                        polyline.Tag = "Vitesse maximum" + tram.VitesseMaxi;
                        polyline.Tag = "Vitesse moyenne" + tram.VitesseMoyenne;


                    };