CODEWITHSUNDEEP
c#asp.net-coreasp.net-core-webapi
Bernard Vander Beken
Bernard Vander Beken

Reputation: 5056

How to validate a required query string field using model validation in ASP.NET Core

Given following API

public class PagedRequest
{
  [Required, Range(1, 100, ErrorMessage = "Limit must be from 1 to 100.")]
  public int Top { get; set; }

  [Required, Range(0, int.MaxValue, ErrorMessage = "Skip must be 0 or greater.")]
  public int Skip { get; set; }
}

[Route("test")]
[HttpGet]
public ActionResult<BarResponse> GetFoos([FromQuery] PagedRequest request)
{
  if (!ModelState.IsValid) return BadRequest(ModelState);

  // Return 200 OK with data here
}

Works as expected:

Doesn't work as expected

Notes:

Upvotes: 7

Views: 3078

Answers (2)

Nick Muller
Nick Muller

Reputation: 2273

It's likely you're missing the ApiController attribute on your Controller class. This attribute applies a couple of default conventions which are common for web APIs, but uncommon for web pages. Although honestly I can't really figure out which convention it is that makes your sample work. It probably has something to do with the model binder.

See: https://learn.microsoft.com/en-us/aspnet/core/web-api/?view=aspnetcore-3.0#apicontroller-attribute

Additionally, with the ApiController attribute you no longer need to check to model state yourself. If the model state is invalid, ASP.NET Core MVC will automatically return a bad request response. So you can remove this part after applying the attribute:

if (!ModelState.IsValid) return BadRequest(ModelState);

Upvotes: 1

Kirk Larkin
Kirk Larkin

Reputation: 93043

You can replace the [Required] attribute with the [BindRequired] attribute, which:

Causes model binding to add a model state error if binding cannot occur for a model's property.

public class PagedRequest
{
    [BindRequired, Range(1, 100, ErrorMessage = "Limit must be from 1 to 100.")]
    public int Top { get; set; }

    [BindRequired, Range(0, int.MaxValue, ErrorMessage = "Skip must be 0 or greater.")]
    public int Skip { get; set; }
}

Upvotes: 5

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