Model validation in ASP.NET Core MVC and Razor Pages

ModelStateInvalidFilter Class

webapi:Create web APIs with ASP.NET Core

Automatic HTTP 400 responses

The[ApiController]attribute makes model validation errors automatically trigger an HTTP 400 response. Consequently, the following code is unnecessary in an action method:

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

ASP.NET Core MVC uses theModelStateInvalidFilteraction filter to do the preceding check.

Default BadRequest response

With a compatibility version of 2.1, the default response type for an HTTP 400 response isSerializableError. The following request body is an example of the serialized type:

{
  "": [
    "A non-empty request body is required."
  ]
}

With a compatibility version of 2.2 or later, the default response type for an HTTP 400 response isValidationProblemDetails. The following request body is an example of the serialized type:

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "traceId": "|7fb5e16a-4c8f23bbfc974667.",
  "errors": {
    "": [
      "A non-empty request body is required."
    ]
  }
}
 

TheValidationProblemDetailstype:

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

Log automatic 400 responses

SeeHow to log automatic 400 responses on model validation errors (aspnet/AspNetCore.Docs #12157).