strange behaviour calling method of wcf from powershell using new-webproxyservice

Question

Can someone explain this to me:

I builded an really simple wcf service for testing purposes.
Consuming service from powershell using New-WebServiceProxy I found

Answer 1

Experimenting with your answer, and then finally discover this answer, it seems all your problems will go away if you simply add [XmlSerializerFormat] to the operation contract, and the method signature will return to normal. At least my problems did when testing against a 2.0 .Net framework and powershell.