ASP.NET Core 2.1 [FromQuery] not getting param

Question

I'm trying to get a param for my WebAPI from a query param using [FromQuery] using ASP.NET Core 2.1. For the the life of me I cannot figure out what I'm doing wrong.

The particular action looks like this:

[Route("api/[controller]/[action]")]
public class AuthController : Controller
{
    [HttpGet]
    [Authorize(Roles = "admin")]
    public async Task<IActionResult> GenerateCode([FromQuery]string email)
    {
        if (String.IsNullOrEmpty(email))
            return new BadRequestObjectResult(new ApiBadRequestResponse(new string[] { "Email is empty." }));

        var result = await _mediator.Send(new CreateAccessCode.Command
        {
            Email = email
        });

        if (result.Succeeded)
            return new OkObjectResult(new ApiOkResponse(result.Data));

        return new BadRequestObjectResult(new ApiBadRequestResponse(result.Errors));
    }
}

email is always null and I've put a breakpoint in the function so I know its getting called.

The request I'm sending is this:

{{url}}/api/auth/generatecode?email=test

If I create a new project from scratch, [FromQuery] seems to work, I have no idea what I'm doing differently. The action is getting called, but is always return BadResponse due to the first line...

My startup.cs function looks like this:

services.AddMvc()
            .SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
            .AddMvcOptions(options =>
            {
                options.Filters.Add(new ActionValidationFilter());
            })
            .AddFluentValidation()
            .AddJsonOptions(options =>
            {
                options.SerializerSettings.ContractResolver =
                new CamelCasePropertyNamesContractResolver();
            })
            .AddSessionStateTempDataProvider();

I'm completely lost. This is the first action I have in my WebAPI that is looking for a query param. All other actions are using FromBody and work fine.

What do you use to submit the data to Web API ? React, Angular, Jquery ? Please mention clearly so I can help you — user4851087
– user4851087, Commented Jul 16, 2018 at 4:08
For now, just using postman to send the request. Removing the HttpPost or switching HttpGet doesn’t change the behavior. — bryken
– bryken, Commented Jul 16, 2018 at 9:03

p3tch · Accepted Answer · 2018-07-16 09:37:44Z

4

Option 1)
Try changing your [HttpGet] attribute to

[HttpGet("GenerateCode/{email}]

You will need to remove /[action] from your controller's Route attribute if doing this, so it'd just be

[Route("api/[controller]")]

Option 2)
Alternatively, in Startup.cs change app.UseMvc(); to

app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "default",
        template: "api/{controller=Home}/{action=Index}/{id?}");
});

And remove [Route("api/[controller]/[action]")] from the controller attributes and make sure you don't have the [ApiController] attribute either

This solution will change your entire project's routing, so you'll have to do the same for all your other API controllers

Option 3)
A third solution would be to change [Route("api/[controller]/[action]")] to

[Route("api/[controller]/[action]/{id?}")]

I have tested all 3 solutions and they all with with the URL {{url}}/api/ControllerName/ActionName?email=test

edited Jul 16, 2018 at 9:37

answered Jul 16, 2018 at 9:11

p3tch

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3 Comments

bryken Over a year ago

I tried each of these solutions and unfortunately, they don't work for me with the URL provided. Option 2 doesn't seem to be an option because my project is purely a WebAPI without a "HomeController". Option 3 also wouldn't seem to work in my case only because there are other actions within the controller (which I left out for brevity) and that would apply to all of them. Option 1 just doesn't seem to work. Its still unclear to me why [FromQuery] doesn't work, especially when I create a new project and it works just fine in that one.

p3tch Over a year ago

@bryken Option 2 is just a template, you don't need an actual Home controller for it to work. Reminder: if you use option 1 you'll still need to edit the route attribute to remove /[action] off the end. Why can't you use option 3? The final {id?} is optional (i.e. {{url}}/api/ControllerName/ActionName would still work fine with option 3)

bryken Over a year ago

I did end up getting this to work. However, I still didn't understand why [FromQuery] wasn't working. I ended up reverting all the changes I made and restarting again, in this case I was able to get the [FromQuery] to work. I wish I knew what happened the first time to provide more insight in case anyone else runs into a similar problem. Thanks for the help.

Jean-Sébastien Gervais · Accepted Answer · 2019-02-28 16:36:28Z

2

A little late answer but may be helpful for others

Option 4

You can explicitly name the querystring parameter name within the [FromQuery] attribute

[HttpGet]
[Authorize(Roles = "admin")]
public async Task<IActionResult> GenerateCode([FromQuery(Name="email")] string email)
{

}

answered Feb 28, 2019 at 16:36

Jean-Sébastien Gervais

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