Pasar parametro a Silverlight

En el aspx:

protected void Page_Load(object sender, EventArgs e)
{
Silverlight1.Load += new EventHandler(Silverlight1_Load);
}

void Silverlight1_Load(object sender, EventArgs e)
{
Silverlight1.InitParameters = "key1=algo";
}

En el app:

string parametro = e.InitParams["key1"];
this.RootVisual = new MainPage(parametro);