how to show the output of a webservice as an XML file

Question

Please anybody explain how to show the output of a web service as an XML file.I have created a web service using MVC 5 and Web API 2.While running the application when I enter the URL I am getting a json file as o/p.Also please tell me how to do actions other than getting all the records using webservice.I mean I want to insert and update records using webservice.Is that possible?Actually I am using most of these technologies for the first time...PLease Help..