I changed the default namespace of my solution and assembly name, but i still get an error that there is abiguity between these even though the latter namespace is no where to be found.
httpHandler.ProcessRequest(HttpContext.Current)
NewName.Controllers.HomeController
OldName.Controllers.HomeController
Changing the default namespace does not automatically change the actual namespaces of existing classes. If you're trying to resolve a namespace conflict that way, you will have to actually change the existing namespaces.
A quick and easy way to do that in Visual Studio is to open up a class, right-click on the first word of the namespace declaration at the top, go to Refactor->Rename, and then type in a new name. That should change the namespace of all existing classes in your project (most of the time).