Get url to web api controller method in the Razor Pages app?

Question

I have the index.cshtml under the /Pages folder. And the web api controller in the same folder:

[Route("api/[controller]")]
[ApiController]
public class ValuesController: ControllerBase
{
    [HttpGet]
    public IEnumerable<string> GetValue(){
        return new string[] { "value1", "value2" };
    }
}

Now I'm expected that this code should work (as it works in Asp Core 2):

var apiUri = Url.Action(action: "GetValue", controller: "Values");
var apiUri2 = Url.ActionLink(action: "GetValue", controller: "Values");

But it doesn't work (return nulls): As well as all other options I have tried :

 var apiUri3 = Url.Action(action: "GetValue", controller: "ValuesController");

How to force Url.Action work for web api controller in CORE 3 (4 and 5)?

Here is the IActionDescriptorCollectionProvider.ActionDescriptors.Items information:

Project structure (actually core web app):

Command window results:

>? Url.Action(action: "GetValue", controller: "Values");
null
>? Url.Action(action: "GetValue", controller: "ValuesController");
null
>? Url.Action(action: "Value", controller: "ValuesController");
null
>? Url.Action(action: "Value", controller: "Values");
null
>

For those who minus as "obvious" (I guess), test youself:

1. [ApiController] commented out (controller is no marked as ApiController); [Route("api/[controller]/[action]")] added; no endpoints.* modifications - is the controller "routable"? (answer "no")
2. still not [ApiController] but now we add endpoints.MapControllerRoute("default", "api/[controller]/[action]"); - is the controller "routable"? (answer "yes")
3. now we additionaly to (2) comment out [Route("api/[controller]/[action]")] - is the controller "routable"? (answer "no")
4. now return [Route("api/[area]/[controller]/[action]")] but also add [ApiController] and add [Area("myarea")] is the controller "routable"? (answer "no")

Answer 1

The reason it does not work its because the routing for ApiController works different.

In your example:

[Route("api/[controller]")]
[ApiController]
public class ValuesController: ControllerBase
{
    [HttpGet]
    public IEnumerable<string> GetValue(){
        return new string[] { "value1", "value2" };
    }
}

Assuming that this in localhost

Really means the route is "http://localhost/api/Values"

if you want for example "http://localhost/api/Values/GetValue" you need to do:

[Route("api/[controller]")]
[ApiController]
public class ValuesController: ControllerBase
{
    [HttpGet("GetValue")]//notice the extra piece of route we added here
    public IEnumerable<string> GetValue()
    {
        return new string[] { "value1", "value2" };
    }

    [HttpGet("GetAnotherValue")]//notice the extra piece of route we added here
    public IEnumerable<string> GetValue()
    {
        return new string[] { "value1", "value2" };
    }
}

As for using Url.Action you might get away with using something like:

///api/Values/GetValue"
var apiUri1 = Url.Action(action: "GetValue", controller: "Values");

///api/Values/GetAnotherValue"
var apiUri2 = Url.Action(action: "GetAnotherValue", controller: "Values");

Finally you need to make sure you mapped the api controller routes

app.UseEndpoints(endpoints =>
{
    endpoints.MapControllers(); // Map attribute-routed API controllers
    //endpoints.MapDefaultControllerRoute(); // Map conventional MVC controllers using the default route
    endpoints.MapRazorPages();//map razor pages
});

Finally your "ApiController" controllers do not need to be in the "Pages" folder. Api controllers route by Attributes not by "folder location". I suggest you put them inside a folder called Controllers in the root of your project.

The other answer in this post seems to "work" but as soon as you add another action to the the API controller you will realize it produces the wrong urls on the Url.Action calls because in ApiControllers the routing does not happen by "Method Name"