405 method not allowed MVC 4 POST was working before - asp.net-mvc

Question

I have a really baffling issue with a customer site. We developed a C# MVC 4.0 application that's running in a subdirectory from another ASP.net application. We use a lot of Ajax calls from JQuery to controllers. Recently there's been an issue where a particular method on a controller has started returning "405 method not allowed" when doing a POST. This method is no different from any of the numerous other Ajax methods which are fine.
Edited to provide code:
Here's the offending function:
JavaScript:
function populateCitiesLike(cityTerm, fnInitialCityNames) {
var serviceBase = 'ProjectCities/';
var cityData = { term: cityTerm };
$.ajax({
type: "POST",
data: JSON.stringify(cityData),
url: serviceBase + "GetCitiesThatStartWith/",
contentType: "application/json",
success: function (result) {
$("#cityCheckboxes").empty();
if (result.length === 0) {
return;
}
addCityCheckboxes(result);
if (fnInitialCityNames != null)
fnInitialCityNames();
},
error: function () {
alert("We have an error");
}
});
}
c# controller :
[AjaxOnly,HttpPost]
public ActionResult GetCitiesThatStartWith(string term)
{
List<string> dbCities = null;
List<Cities> cityList = new List<Cities>();
dbCities = _reposProject.GetCitiesThatStartWith(term);
cityList = GetJsonFormatForCityList(dbCities);
// return Json(result);
return Json(cityList, JsonRequestBehavior.AllowGet);
}
I copied the entire web application and created a new subdirectory just to see what would happen. So for example the current application is running under main\A directory and now the cloned application is running under main\B. the method GetCitiesThatStartWith running under main\A that returns a 405 but the same method under main\B works. However there is one specific method called GetCitiesFromRegion that is always failing on both. That particular method used to work.
I don't think it's a code issue because why would one work and the other not. Resetting IIS does not work either. I can add test methods to the controller and call them from a test Ajax page and sometimes they fail and sometimes not. Once they fail with that particular method name I can no longer make it work. It's almost as if IIS remembers that the method failed and is caching the error.
updated
After spending more time with it I have discovered 2 issues. One issue is that the controllers constructor was throwing an exception because it was not authenticated at that point. I have resolved that issue.
The other issue which is baffling is that I could not get GetCitiesThatStartWith to work and a few other methods. I renamed them by appending V2 to the end of the method name and now they work.
Why would renaming a method on a controller make it work? I suspect that once the method gets an error and it stops working then I have to rename the method. Something about throwing an exception in the controller can be fatal to your method name apparently.

Answer 1

I think this will help you:-
I have changed the method name to CitiesThatStartWith by default it will be mapped with Get request because you are using GetCitiesThatStartWith.
Controller code
[AjaxOnly,HttpPost]
public ActionResult CitiesThatStartWith(string term)
{
List<string> dbCities = null;
List<Cities> cityList = new List<Cities>();
dbCities = _reposProject.GetCitiesThatStartWith(term);
cityList = GetJsonFormatForCityList(dbCities);
// return Json(result);
return Json(cityList, JsonRequestBehavior.AllowGet);
}
Javascript code
function populateCitiesLike(cityTerm, fnInitialCityNames) {
var serviceBase = 'ProjectCities/';
var cityData = { term: cityTerm };
$.ajax({
type: "POST",
data: JSON.stringify(cityData),
url: serviceBase + "CitiesThatStartWith/",
contentType: "application/json",
success: function (result) {
$("#cityCheckboxes").empty();
if (result.length === 0) {
return;
}
addCityCheckboxes(result);
if (fnInitialCityNames != null)
fnInitialCityNames();
},
error: function () {
alert("We have an error");
}
});
}