ASP.NET Core - Required query string parameters

Typically when designing your API, query string parameters should be reserved for optional arguments.

So for example if ID is a required parameter, it is better to use this as the URI:

https://example.api.com/product/1234

instead of this:

https://example.api.com/product?id=1234

where 1234 is the ID of the requested product.

Of course there are always exceptions and I had a situation where I wanted to use a required query parameter.

ASP.NET Core can help you there by using the [Required] or [BindRequired] attributes on your action method parameters:

	[ApiController]
	[Route("[controller]")]
	public class ProductController : ControllerBase
	{
	[HttpGet]
	public IActionResult Get([Required] int id) => Ok();
	}

view raw ProductController1.cs hosted with ❤ by GitHub

	[ApiController]
	[Route("[controller]")]
	public class ProductController : ControllerBase
	{
	[HttpGet]
	public IActionResult Get([BindRequired] int id) => Ok();
	}

view raw ProductController2.cs hosted with ❤ by GitHub

Both controllers will return a validation error when invoked without the id parameter:

	{
	"type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
	"title": "One or more validation errors occurred.",
	"status": 400,
	"traceId": "|7fb5e16a-4c8f23bbfc974667.",
	"errors":{
	"Id":[
	"A value for the 'Id' parameter or property was not provided."
	]
	}
	}

view raw Response.json hosted with ❤ by GitHub