Use custom validation responses with fluent validation

Question

Hello I am trying to get custom validation response for my webApi using .NET Core.

Here I want to have response model like

[{
  ErrorCode:
  ErrorFi         


        

Answer 1

As for me, it's better to use the following code in ASP.NET Core project

  services.AddMvc().ConfigureApiBehaviorOptions(options =>
  {
    options.InvalidModelStateResponseFactory = c =>
    {
      var errors = string.Join('\n', c.ModelState.Values.Where(v => v.Errors.Count > 0)
        .SelectMany(v => v.Errors)
        .Select(v => v.ErrorMessage));

      return new BadRequestObjectResult(new
      {
        ErrorCode = "Your validation error code",
        Message = errors
      });
    };
  });

Also take into account that instead of anonymous object you can use your concrete type. For example,

     new BadRequestObjectResult(new ValidationErrorViewModel
      {
        ErrorCode = "Your validation error code",
        Message = errors
      });