WebApi Multiple actions were found with GetAll() and GetByIds(int[] ids)

Question

Using the standard route:

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

With these actions:

public class ValuesController : ApiController
{
    // GET api/values
    public string GetAll()
    {
        return "all";
    }

    // GET api/values/5
    public string GetById(int id)
    {
        return "single";
    }

    // GET api/values?ids=1&ids=2
    public string GetByIds([FromUri] int[] ids)
    {
        return "multiple";
    }

And make a request to /api/values, I get this exception:

Multiple actions were found that match the request: 
System.String GetAll() on type MvcApplication4.Controllers.ValuesController
System.String GetByIds(Int32[]) on type MvcApplication4.Controllers.ValuesController

I've been spinning my wheels trying to find a solution around this. It's my belief that the GetAll and GetByIds actions are considered Multiple here, but they aren't because the GetByIds has a different signature.

Is there a work around for this that doesn't involve adding {action} to the route?

Answer 1

Thanks for the input everyone. After kicking options around, the only way I found to do this, is to combine the GetAll and GetByIds action and switch case the length of ids.

public class ValuesController : ApiController
{
    // GET api/values/5
    public string GetById(int id)
    {
        return "single";
    }

    // GET api/values
    // GET api/values?ids=1&ids=2
    public string GetByIds([FromUri] int[] ids)
    {
        switch (ids.Length)
        {
            case 0:
                return "all";

            default:
                return "multiple";
        }
    }

Answer 2

We currently do not have out of box support for binding collection of values coming from Uri. Following is the issue regarding that and also the action disambiguation problem:

http://aspnetwebstack.codeplex.com/workitem/322

Unfortunately, i cannot think of a work around related to the Action selection problem(without the '{action}') itself even though you solve the problem of modelbinding to collection using a custom parameter binding like below:

public string GetByIds(int[] ids)
    {
        return "multiple";
    }
------------------------

config.ParameterBindingRules.Insert(0, typeof(int[]), (paramDesc) => new SampleParameterBinding(paramDesc));

-------------------------

public class SampleParameterBinding : HttpParameterBinding
{
    public SampleParameterBinding(HttpParameterDescriptor desc)
        : base(desc)
    {
    }

    public override bool WillReadBody
    {
        get
        {
            return false;
        }
    }

    public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken)
    {
        HttpRequestMessage currentRequest = actionContext.Request;

        NameValueCollection nvc = currentRequest.RequestUri.ParseQueryString();

        //TODO: ERROR CHECKS
        int[] ids = nvc["ids"].Split(',').Select(str => Int32.Parse(str)).ToArray();

        // Set the binding result here
        SetValue(actionContext, ids);

        // now, we can return a completed task with no result
        TaskCompletionSource<AsyncVoid> tcs = new TaskCompletionSource<AsyncVoid>();
        tcs.SetResult(default(AsyncVoid));
        return tcs.Task;
    }

    private struct AsyncVoid
    {
    }
}

Answer 3

I'd recommend attribute routing:

[RoutePrefix("api")]
public class ValuesController : ApiController
{
    // GET api/values
    // GET api/values?ids=1&ids=2
    [Route("values")]
    public string GetCollection([FromUri] IList<int> ids)
    {
        if (ids == null)
        {
          return "all";
        }
        return "multiple";
    }

    // GET api/values/5
    [Route("values/{id:int}")]
    public string GetById(int id)
    {
        return "single";
    }