Problem with endpoint routing in ASP.NET Web API (.NET Core 3.1)

Question

Good afternoon,

I'm having some trouble with endpoint routing in my web API using attribute routing and the ASP.NET core routing middleware.

I have an API controller that looks roughly like the following:

public class UsersController : ControllerBase
{
    [HttpGet]
    [Route("v1/users/{id}", Name = nameof(GetUser), Order = 1)]
    public async Task<ActionResult> GetUser([FromQuery(Name = "id")] string userGuid)
    {
       // Implementation omitted.
    }

    [HttpGet]
    [Route("v1/users/me", Name = nameof(GetCurrentUser), Order = 0)]
    public async Task<ActionResult> GetCurrentUser()
    {
        // Implementation omitted.
    }
}

I am trying to configure the endpoint routing so that requests for 'v1/users/me' are routed to the 'GetCurrentUser()' method, while requests matching the template 'v1/users/{id}' (where {id} != me) are routed to the 'GetUser()' method. I was hoping that this could be solved by placing the 'v1/users/me' endpoint before the other endpoint in the endpoint order, but it seems the order parameter isn't respected by the routing middleware. I've also tried explicitly mapping the 'v1/users/me' endpoint before mapping the remaining endpoints, but this doesn't seem to work either.

Here is the current startup configuration:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
   if (env.IsDevelopment())
   {
       app.UseDeveloperExceptionPage();
   }

   app.UseHttpsRedirection();
   app.UseStaticFiles();
   app.UseResponseCompression();
   app.UseRouting();
   app.UseAuthentication();
   app.UseAuthorization();

   app.UseEndpoints(endpoints =>
   {
       // Explicit mapping of the GetCurrentUser endpoint - doesn't seem to do anything.
       // endpoints.MapControllerRoute("v1/users/me", "Users/GetCurrentUser");

       endpoints.MapControllers();
   }
}

Is this possible to achieve with attribute routing, and if so, what am I missing?

Thanks!

Answer 1

This should already work fine if you just leave the defaults like this:

[HttpGet("v1/users/{id}")]
public async Task<ActionResult> GetUser(string id)
{
    return Ok(new { id = id });
}

[HttpGet("v1/users/me")]
public async Task<ActionResult> GetCurrentUser()
{
    return Ok(new { id = "current" });
}

With attribute routing, routes that contain constant parts are favored over routes that contain a route variable at the same location. So v1/users/me is ranked higher than v1/users/{id} with id = "me", so you should see the GetCurrentUser run when you access that route. This is regardless of method ordering within your controller.

Answer 2

The issue was with the annotation of the API endpoint methods.

I mistakenly marked the parameter in the GetUser(string id) endpoint with the [FromQuery] attribute rather than the [FromRoute].

The following works as expected:

public class UsersController : ControllerBase
{
    [HttpGet]
    [Route("v1/users/{id}", Name = nameof(GetUser))]
    public async Task<ActionResult> GetUser([FromRoute(Name = "id")] string userGuid)
    {
       // Changed from [FromQuery(Name = "id")] to [FromRoute(Name = "id")]

       // Implementation omitted.
    }

    [HttpGet]
    [Route("v1/users/me", Name = nameof(GetCurrentUser))]
    public async Task<ActionResult> GetCurrentUser()
    {
        // Implementation omitted.
    }
}