Before "using" it, you have to have this class in your code; this is your immediate problem. First, the full class name is
System.ServiceModel.Activation.ServiceRoute
. Second, I'm not sure that you even referenced the assembly where that class is found. This is "System.ServiceModel.Activation.dll":
ServiceRoute Class (System.ServiceModel.Activation)[
^].
The assembly is in GAC; with Visual Studio, the reference is added from the first tab of the window "Add Reference".
—SA