Optional Parameters in Web Api Attribute Routing
asp.net, asp.net-web-api, asp.net-web-api-routing, c#
Solution
For an incoming request like `/v1/location/1234`, as you can imagine it would be difficult for Web API to automatically figure out if the value of the segment corresponding to '1234' is related to `appid` and not to `deviceid`.
I think you should change your route template to be like `[Route("v1/location/{deviceOrAppid?}", Name = "AddNewLocation")]` and then parse the `deiveOrAppid` to figure out the type of id.
Also you need to make the segments in the route template itself optional otherwise the segments are considered as required. Note the `?` character in this case. For example: `[Route("v1/location/{deviceOrAppid?}", Name = "AddNewLocation")]`
Problem
I want to handle POST of the following API-Call: `/v1/location/deviceid/appid` Additional Parameter are coming from the Post-Body. This all works fine for me. Now I wnat to extend my code by allowing "deviceid" and/or "appid" and/or BodyData to be null: ``` /v1/location/deviceid /v1/location/appid /v1/location/ ``` These 3 URLs should responded by the same route. My first approach (BodyData required): ``` [Route("v1/location/{deviceid}/{appid}", Name = "AddNewLocation")] public location_fromuser Post(string deviceid = null, string appid = null, [FromBody] location_fromuser BodyData) { return repository.AddNewLocation(deviceid, appid, BodyData); } ``` This does not work and returns a compile error: "optional Parameters must be at the end" Next try: ``` [Route("v1/location/{deviceid}/{appid}", Name = "AddNewLocation")] public location_fromuser Post([FromBody] location_fromuser BodyData, string deviceid = null, string appid = null) ``` Now my function AddNewLocation() get always an `BodyData=null` - even if the call send the Body. Finally I set all 3 Parameter optional: ``` [Route("v1/location/{deviceid}/{appid}", Name = "AddNewLocation")] public location_fromuser Post(string deviceid = null, string appid = null, [FromBody location_fromuser BodyData = null) ``` Don´t work: Optional parameter `BodyData` is not supported by `FormatterParameterBinding`. Why do I want a solution with optional Parameters? My Controller handles just the "adding of a new Location" via a POST. I want to send on wrong data my own exceptions or error messages. Even if the call has missing values. In this case I want to be able to decide to throw an exception or Setting Defaults by my code.