.Net Core Web API: How to return a validation message from API method?

Question

I am using React Js in my client-side and .Net Core 3.0 Web API on the server-side. I have one API method called CreateAccount and the return type is IActionResult. Now if I do validate with any one of the model property then I have to send or return the validation message along with empty model data. I am new to API and tried like below but could not send the string as a result type.

API method,

[AllowAnonymous]
[HttpPost("createaccount")]
public async Task<IActionResult> CreateAccount([FromBody]Users user)
{
        try
        {
            if (ModelState.IsValid)
            {
                if (user == null)
                    return BadRequest(new { message = "Data is empty" });

                if(user.UserType!="Admin")
                {
                    return new ValidationResult("Only Admin can create new account");
                }
                return Ok(await _userService.CreateAnUserAccount(user));
            }
        }
        catch(Exception e)
        {
            throw new ArgumentException(e.Message);
        }

        return ValidationProblem();
}

I do not know the proper .Net Core API coding part, could anyone please help me to resolve this issue?

mm8 · Accepted Answer · 2020-04-22 09:42:18Z

1

You could return an ObjectResult with a StatusCode other than StatusCodes.Status200OK and a serialized object that contains whatever information you want to return to the client, e.g.:

return new ObjectResult(new YourApiError() { Message = "message.." })
{ 
     StatusCode = StatusCodes.Status405MethodNotAllowed 
};

edited Apr 22, 2020 at 9:42

answered Apr 22, 2020 at 9:15

mm8

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5 Comments

Md Aslam Over a year ago

What I should give for the "YourApiError"?

mm8 Over a year ago

@MdAslam: It's a simple POCO class with a Message property that you define yourself: public class YourApiError { public string Message { get; set; } }

Md Aslam Over a year ago

Yeah thank you for that but I wanted to check the result also. If the result is proper then I have to send the result with statusCode but If any error in the service class then I have to return the validation message. So I have to do it with implicit logic? See my code again that if(user.UserType!="Admin") { return new ValidationResult("Only Admin can create new account"); }

mm8 Over a year ago

@MdAslam: I am not sure I understand your issue. Of course you need to return a different kind of result based on the outcome of your controller action's validation logic.

Md Aslam Over a year ago

Why we can not use the HttpResponseMessage in .Net Core? I think by using this return type "HttpResponseMessage", we can send either error message or success message along with our model data, so I tried to use this HttpResponseMessage but not able to create the response. Can you help on this if any idea on HttpResponseMessage?

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