Web Api GET with arguments

Question

Is it possible to have a route like the following:

MyApi/v1/Events // gets all the events from the db

MyApi/v1/Events?Longitude=4.4777&Latitude=51.9244 //get request for a specific location

In my code, I use attribute based routing with a route prefix:

 [Route("")] // GET: MyApi/v1/Events public IEnumerable<EventDto> Get() { return EventService.GetAllEvents().ToDto(); } [Route("{Latitude}/{Longitude}/{Radius}")] // GET: MyApi/v1/Events?Latitude={doubleVal}&Longitude={doubleVal} public IEnumerable<EventDto> Get(double? Latitude, double? Longitude, double? Radius) { return EventService.ReadEvent(Latitude.Value, Longitude.Value, Radius.Value).ToDto(); }

Also, I use a route prefix on the controller:

[RoutePrefix(WebApiConfig.ClientAppName + "/v1/Events")]

It seems only the Get all and not the parameter version of my api is triggered. I tried different variants of the Route attribute with no success. In my WebApiConfig:

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

If you intend that latitude, longitude and radius identify a specific location, it should be part of the URL path rather than the query string. If route /a/b/c returns a list of something, then /a/b/c?foo=blah should also return a list of something, filtered to entities that satisfy the query string. — user47589
– user47589, Commented Sep 26, 2017 at 21:26

Moho · Accepted Answer · 2017-09-26 21:08:37Z

Your parameterized method expects the route MyApi/v1/Events/{Latitude}/{Longitude}/{radius} (i.e. the parameter values are in the path itself) but your request using the query string parameters maps to route MyApi/v1/Events.

Either format the request to include the parameters in the path or include the parameters in your default Get() action method with null default values and determine which EventService method to call based on the presence of values for those parameters.

Sascha Gottfried · Accepted Answer · 2017-09-27 21:09:08Z

Obviously you want to explore the opportunities of Attribute Routing in ASP.NET Web API 2 to support certain URI patterns that are common in RESTful APIs.

Your specific use case to enable API clients to query the event resource collection based on latitude, longitude and radius is even supported by what is nowadays called convention-based routing.

https://{base_uri}/MyApi/v1/Events?Longitude=4.4777&Latitude=51.9244

public EventsController : ApiController { public IEnumerable<EventDto> GetEvents([FromUri] double? latitude, [FromUri] double? longitude) { //code validating method parameters return EventService.ReadEvent(Latitude.Value, Longitude.Value).ToDto() } }

Using [FromUri] attributes on action parameters is called "Parameter binding". Parameter binding can be useful if you want to force ASP.NET Web API to read a complex type from the URI. Your application is about Events and geospatial concerns and encapsulating these concerns into complex types as you already did with events helps documenting any interface constraints. What would be the meaning of a query for events when only a value for longitude is provided? Given that omitting nullable parameters helps in your specific use case.

The following example defines a GeoPoint type, along with a controller method that gets the GeoPoint from the URI.

public class GeoPoint { public double Latitude { get; set; } public double Longitude { get; set; } } public EventsController : ApiController { //action is only selected when URI contains required parameters to bind a GeoPoint instance public IEnumerable<EventDto> GetEvents([FromUri] GeoPoint geoPoint) { //how about passing a complex type to the EventService? return EventService.ReadEvent(geoPoint).ToDto() } }

A URI returning a collection of events within a given distance/radius could be like

https://{base_uri}/MyApi/v1/Events?Longitude=4.4777&Latitude=51.9244&Radius=10.000

public class GeoPoint { public double Latitude { get; set; } public double Longitude { get; set; } } public class GeoPointQuery { public double Latitude { get; set; } public double Longitude { get; set; } public double Radius {get; set; } } public EventsController : ApiController { public IEnumerable<EventDto> GetEvents([FromUri] GeoPoint geoPoint) { //how about passing a complex type to the EventService? return EventService.GetEventAtPoint(geoPoint).ToDto() } public IEnumerable<EventDto> GetEventsQuery([FromUri] GeoPointQuery geoPointQuery) { //how about passing a complex type to the EventService? return EventService.GetEventsWithinDistance(geoPointQuery).ToDto() } }

Applying Attribute routing will help you addressing more hierarchical URI patterns and has a powerful language to define route constraints.

Thank you for your detailed response and the interesting points made :) I will try it out and get back to you.

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