JSON response from identity registration format

Question

I've added fluent validation to a WebApi project which works fine, i get the following JSON response as an example of user registration:

{
    "errors": {
        "Email": [
            "'Email' is not a valid email address."
        ],
        "Password": [
            "'Password' must contain at least one uppercase, lowercase, number and symbol"
        ]
    },
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "8000003d-0000-fc00-b63f-84710c7967bb"
}

I'm adding validation if a users email already exists. The format of the error response is very different, i need it the same format to catch the error at the client side.

Error model class:

  public class ErrorResponse
  {
     public List<ErrorModel> Errors { get; set; } = new List<ErrorModel>();
  }
  public class ErrorModel
  {
     public string FieldName { get; set; }
     public string Message { get; set; }
  }

Register controller:

   var authResponse = await _identityService.RegisterAsync(request);

        if (!authResponse.Success)
        {
            var errorResponse = new ErrorResponse();

            var errorModel = new ErrorModel
            {
                FieldName = "User",
                Message = "A user exists"
            };

            errorResponse.Errors.Add(errorModel);


            return BadRequest(errorResponse);

        }

JSON response:

{
    "errors": [
        {
            "fieldName": "User",
            "message": "A user exists"
        }
    ]
}

Answer 1

You can use a dictionary for that:

 public class ErrorResponse
  {
     public Dictionary<string,List<string>> Errors { get; set; } = new Dictionary<string,List<string>>();
  }

And add values like this :

errorResponse.Add("User",new List<string>{"A user exists"});