How to have the same response format for 400 response raised from BadRequest and validations?

user_1779091 0
Viewed 344

I have a DTO which is an input param for the API's POST endpoint.

The DTO has got data annotations and validation happens automatically. Following is an example:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "00-f14406a8950b1005234cc79298a79586-77222ebbed97e453-00",
    "errors": {
        "Email": [
            "The Email field is not a valid e-mail address."
        ]
    }
}

However, when I want to raise 400 response from the controller, using either of the following:

return BadRequest("some message")

This returns some message

Where as this: return BadRequest(new { message = "some message"}); returns:

{
    "message": "some message"
}

How to ensure that the same format is used throughout? Is there any in-built way to standardize.

.net-6.0 asp.net-web-api .net c#
2 Answers

As per documentation - https://docs.microsoft.com/en-us/aspnet/core/web-api/?view=aspnetcore-6.0#default-badrequest-response

The ValidationProblemDetails type:

  • Provides a machine-readable format for specifying errors in web API responses.
  • Complies with the RFC 7807 specification.

To make automatic and custom responses consistent, call the ValidationProblem method instead of BadRequest.

ValidationProblem returns a ValidationProblemDetails object as well as the automatic response.

Example:

ModelState.AddModelError("Name", "Invalid name");
return ValidationProblem(ModelState);

You can use this concept across all response codes - for example - instead of 400 (default for ValidationProblem), you can return 401 with the above code by replacing the last line with the following:

return ValidationProblem(modelStateDictionary:ModelState, statusCode:401)

If however you don't want to use this response format and want to have your own then you must disable the middleware that is responsible for automatic model validation and 400 response:

In program.cs:

builder.Services.AddControllers()
    .ConfigureApiBehaviorOptions(options =>
    {
        options.SuppressModelStateInvalidFilter=true;
    });

Now in the controller you will have to do the validations yourself (example: check for nulls) and return BadRequest(new {error = "type something here"};

user_17790910

Create a base api controller as follows:

[ApiController]
public abstract class ApiControllerBase : ControllerBase
{        
    protected virtual IActionResult InvalidModelState() {
        return HttpContext.RequestServices.GetService<IOptions<ApiBehaviorOptions>>()
            .Value.InvalidModelStateResponseFactory(ControllerContext);
    }
}

And derive your api controllers from the ApiControllerBase. Whenever you want to add errors and use the same format of validation errors just add a ModelState.AddModelError("", "Your error message") then return InvalidModelState();.

user_178497660
Related