If you want to return a json string from your action which adheres to camelcase notation what you have to do is to create a JsonSerializerSettings instance and pass it as the second parameter of JsonConvert.SerializeObject(a,b) method.
public string GetSerializedCourseVms()
{
var courses = new[]
{
new CourseVm{Number = "CREA101", Name = "Care of Magical Creatures", Instructor ="Rubeus Hagrid"},
new CourseVm{Number = "DARK502", Name = "Defence against dark arts", Instructor ="Severus Snape"},
new CourseVm{Number = "TRAN201", Name = "Transfiguration", Instructor ="Minerva McGonal"}
};
var camelCaseFormatter = new JsonSerializerSettings();
camelCaseFormatter.ContractResolver = new CamelCasePropertyNamesContractResolver();
return JsonConvert.SerializeObject(courses, camelCaseFormatter);
}