Always getting 404 when passing an array to a .Net Core Web API method

Question

I cannot seem to pass an array of values to my Web API method for some reason. Here is my code:

[HttpGet("api/values/get/{ids}")]
public JsonResult GetValues(string[] valueIds)
{
   //Do something
}

I have tried calling this via the following URLs:

When I call it via the following URLs, I get no 404 and the method is actually called, however, the array is empty:

I have also tried adding the Attribute [FromQuery] to the front of my parameters in the method signatures like this:

public JsonResult GetValues([FromQuery]string[] valueIds)

I cannot seem to get it to work even though every tutorial out there says it should. Ripping my hair out here.

https://stackoverflow.com/questions/9981330/pass-an-array-of-integers-to-asp-net-web-api — Daniel A. Thompson, Jan 22 '18 at 17:12
I have tried the exact same URL from the accepted answer on that post (It's the third one in my question) — LeonidasFett, Jan 22 '18 at 17:14

score 3 · Accepted Answer · answered Jan 22 '18 at 17:18

3

Remove {ids} prefix because the action selector expects ids parameter but you don't pass it in the action.

[HttpGet("api/values/get")]
public JsonResult GetValues(string[] valueIds)
{
   //Do something
}

And apply the request like this;

http://localhost:5001/api/values/get?valueIds=das&valueIds=ewq

answered Jan 22 '18 at 17:18

lucky

This works. But I don't understand why it works when I pass only a single parameter. For example: [HttpGet("api/values/get/byparent/{parentId}")]. When I call this method with the URL http://localhost:5001/api/values/byparent/dsadasda, the method gets called and the parameter is passed. – LeonidasFett Jan 22 '18 at 17:25
"dsadasda" is passed as "parentId" parameter. But in the question case, there is no parameter with named "ids". – lucky Jan 22 '18 at 17:27

score 1 · Answer 2 · answered Jan 22 '18 at 17:21

So let's break appart what you have:

[HttpGet("api/values/get/{ids}")]
public JsonResult GetValues(string[] valueIds)
{
   //Do something
}

I would reccomend removing the /get because your method of request is get in HttpGet
Your specified route implies a passed ids(it's just a variable same as get it can only be singular) i.e:

The examples that you have shown.

get/?valueIds=das&valueIds=ewq doesn't even specify{ids}

so far your route of /get/{ids} is redundant.

Try

[HttpGet("api/values")]
public JsonResult GetValues(string[] valueIds)
{
   //Do something
}

I'd recommend to read up on REST API naming conventions

score 0 · Answer 3 · answered Jan 22 '18 at 17:13

Correct me if I am wrong but I think you need to name the query params with the []-Suffix. Like that:

http://localhost:5001/api/values/get?valueIds[]=das&valueIds[]=ewq

Otherwise you can easily check what your API except with the UrlHelper. Just generate yourself an url:

var url = Url.Action("GetValues", new { valueIds = new [] { "das", "ewq" } });

3 Answers3