All ASP.NET Web API controllers return 404

I have been working on a problem similar to this and it took me ages to find the problem. It is not the solution for this particular post, but hopefully adding this will save someone some time trying to find the issue when they are searching for why they might be getting a 404 error for their controller.

Basically, I had spelt "Controller" wrong at the end of my class name. Simple as that!

Had essentially the same problem, solved in my case by adding:

<modules runAllManagedModulesForAllRequests="true" />

to the

<system.webServer>

</system.webServer>

section of web.config

Add following line

GlobalConfiguration.Configure(WebApiConfig.Register);

in Application_Start() function in Global.ascx.cs file.

One thing I ran into was having my configurations registered in the wrong order in my GLobal.asax file for instance:

Right Order:

AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);

Wrong Order:

AreaRegistration.RegisterAllAreas();
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
WebApiConfig.Register(GlobalConfiguration.Configuration);

Just saying, this was my problem and changing the order is obvious, but sometimes overlooked and can cause much frustration.