Q:

Can't bind params using [FromQuery] ASP Net Core 2 API

I'm new in ASP Net Core 2, I want to bind different parameters that come from URL query string to action parameters in my action:
[HttpGet("{page}&{pageSize}&{predicate}", Name = "GetBuildingsBySearchCriteria")]
public IActionResult GetBuildingsBySearchCriteria([FromHeader] string idUser, [FromQuery]int page, [FromQuery]int pageSize, [FromQuery]string predicate)
{
    ....
}

When I test my action using postman, I set the idUser in header and other parameters in URL, example: 
http://localhost:51232/api/buildings/page=1&pageSize=10&predicate=fr

The result is that I receive the idUser that I send from the header but other parameters are empty.
Do I miss something or what is wrong in my code?

A:

If those parameter are meant to be in the query then there  is no need for them in the route template
In 
[HttpGet("{page}&{pageSize}&{predicate}", Name = "GetBuildingsBySearchCriteria")]

"{page}&{pageSize}&{predicate}" are placeholders in the route template, which is why the [FromQuery] fails to bind the parameters.

[FromHeader], [FromQuery], [FromRoute], [FromForm]: Use these to specify the exact binding source you want to apply.

emphasis mine
Based on the example URL shown and assuming a root route, then one option is to use
[Route("api/[controller]")]
public class BuildingsController: Controller {

    //GET api/buildings?page=1&pageSize=10&predicate=fr
    [HttpGet("", Name = "GetBuildingsBySearchCriteria")]
    public IActionResult GetBuildingsBySearchCriteria(
        [FromHeader]string idUser, 
        [FromQuery]int page, 
        [FromQuery]int pageSize, 
        [FromQuery]string predicate) {
        //....
    }
}

or alternatively you can use them in the route like
[Route("api/[controller]")]
public class BuildingsController: Controller {

    //GET api/buildings/1/10/fr
    [HttpGet("{page:int}/{pageSize:int}/{predicate}", Name = "GetBuildingsBySearchCriteria")]
    public IActionResult GetBuildingsBySearchCriteria(
        [FromHeader]string idUser, 
        [FromRoute]int page, 
        [FromRoute]int pageSize, 
        [FromRoute]string predicate) {
        //....
    }
}

Reference Model Binding in ASP.NET Core

