Seems like you mentioned the class name as "App+Main" which is incorrect. You have to provide the "Namespace.Class Name". Also, it is not recommended to create the custom match rule on Main method, because this method will get invoke only one time in the application life time. So, please create the rules on a method which will get invoked much frequently (which executes the actual transactions like get users, get data from some service etc.,) i.e. more than 2 times in the application life time.