ASP.NET Web API actions - only one GET per controller?

Question

I'm new to ASP.NET Web API but I'm hitting an issue where if I'm trying to add two get methods to a single controller it is failing at trying to get the action. Are we allowed only one get per controller, unless we are adding an overload of the same method?

This works if I only have one get method, e.g. the first one. As soon as I add Get to the second method name, it gives me a 500.

[HttpGet]
public string GetToday()
{
    return "Hello today";
}

[HttpGet]
public string GetPending()
{
    return "Hello Pending";
}

The calls I'm making: http://abc.com/api/tasks/gettoday http://abc.com/api/tasks/getpending

I can make this call if the method name is just 'Today', as long as I put the [HttpGet] attribute. But only if I don't have the second action. Which means if I remove the [HttpGet] attribute from the second method as well as remove 'Get' from the method name so it is just Pending, then it works.

As soon as there are two get methods I get this error:

{"Message":"An error has occurred.","ExceptionMessage":"Multiple actions were found that match the request: \r\nSystem.String TodaysTasks() on type TaskTrackerService.Controllers.TasksController\r\nSystem.String PendingTasks() on type TaskTrackerService.Controllers.TasksController","ExceptionType":"System.InvalidOperationException","StackTrace":" at System.Web.Http.Controllers.ApiControllerActionSelector.ActionSelectorCacheItem.SelectAction(HttpControllerContext controllerContext)\r\n at System.Web.Http.Controllers.ApiControllerActionSelector.SelectAction(HttpControllerContext controllerContext)\r\n at System.Web.Http.ApiController.ExecuteAsync(HttpControllerContext controllerContext, CancellationToken cancellationToken)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsyncInternal(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)"}

You can have as many actions as you want. Can you post code? — jchapa
can you show what actions you're trying? You can only have one GET with the same method signature, but any number of actions with various names or signatures (and routes pointing to them) — Brad Christie
Please post some code showing your controller actions AND your route configuration — levelnis
This is ASP.NET Web API and not MVC, so I will edit the question as such. — Eilon
I figured it out - the default config is webapiconfig and not routeconfig, and instead of {controller}/{action}/{id} it had api/{controller}/{id}. When I added action there it worked great. It makes sense now. Thanks! — raleign

Cornelius Cornelius · Accepted Answer · 2014-07-23T13:59:35

The idea behind a Web API is that it represents a ReSTful resource. The semantics of ReST imply that a controller corresponds to the idea of a 'resource' and that behaviour is determined by the HTTP verb used to access the resource — means GET, POST, PUT, DELETE, …

The model used for these resources is that you treat them somewhat "CRUD-y"; that you query for elements of the resource, put new elements into the resource, update elements in the resource – you get the idea.

For each (relevant) verb you should have only one action that deals with requests of that nature. The idea of having multiple actions accessed by GET is not very ReSTful and more a MVC-ish RPC-style mode of thinking that is not well-suited for ASP.NET Web API.

So your controller might instead be written:

public class FooController : ApiControlle
{
    [HttpGet]
    public Account Get(string flavour)
    {
        switch (flavour) {
            case "greeting": return "Hello today";
            case "pending": return "Hello Pending";
            default: throw new InvalidOperationException("Cannot get your flavour of foo :(");
        }
    }
}

But as you have written in a comment, the trouble was that you never intended to use the controller as Web API controller, but MVC controller.

ASP.NET Web API actions - only one GET per controller?

1 Answers