Response to missing required Properties in ASP.NET Core

问题

Given the following controller:

using System.ComponentModel.DataAnnotations;
using Microsoft.AspNetCore.Mvc;

namespace WebApplication1.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ValuesController : ControllerBase
    {
        // POST api/values
        [HttpPost]
        public ActionResult<string> Post([FromBody] Model req)
        {
            return $"Your name is {req.Name}";
        }
    }

    public class Model
    {
        [Required] public string Name { get; set; }
    }
}

if I post an empty body {}, the response is:

{
    "errors": {
        "Name": [
            "The Name field is required."
        ]
    },
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "80000002-0002-ff00-b63f-84710c7967bb"
}

I would like to change this response, so it becomes easier to automatically pass the error message on to the user. So I would like it to look more like this:

{
    "error": 999,
    "message": "Field 'name' is required."
}

I tried to extend the RequiredAttribute-class like so:

public class MyRequiredAttribute : RequiredAttribute
{
    public MyRequiredAttribute()
    {
        ErrorMessage = "{0} is required";
    }
}

which sadly only changes the returned string in the collection, like so

{
    "errors": {
        "Name": [
            "Name is required"
        ]
    },
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "80000006-0000-ff00-b63f-84710c7967bb"
}

回答1:

When utilizing a controller with the ApiController attribute applied, ASP.NET Core automatically handles model validation errors by returning a 400 Bad Request with ModelState as the response body. It is related to Automatic HTTP 400 responses . You could customize BadRequest response like below :

  services.AddMvc()
                .ConfigureApiBehaviorOptions(options =>
                {
                    options.InvalidModelStateResponseFactory = actionContext =>
                    {
                        var modelState = actionContext.ModelState;
                        return new BadRequestObjectResult(FormatOutput(modelState));
                    };
                })
                .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

Customize the FormatOutput method to your whims.

public List<Base> FormatOutput(ModelStateDictionary input)
    {
        List<Base> baseResult = new List<Base>();
        foreach (var modelState in input.Values)
        {
            foreach (ModelError error in modelState.Errors)
            {
                Base basedata = new Base();
                basedata.Error = StatusCodes.Status400BadRequest;
                basedata.Message =error.ErrorMessage; 
                baseResult.Add(basedata);
            }
        }
        return baseResult;
    }

public class Base
{
    public int Error { get; set; }
    public string Message { get; set; }
}

回答2:

Try and add this code below the [Requried] annotation

[StringLength(150, ErrorMessage = "Name length can't be less than 1 or greater than 150 characters.", MinimumLength = 1)]

Hope this helps...

来源：https://stackoverflow.com/questions/57233662/response-to-missing-required-properties-in-asp-net-core

标签

validation

asp.net-core