Handle ModelState Validation in ASP NET Web API

Question

I was wondering how I can achieve model validation with ASP NET Web API  I have my model like so   public class Enquiry        Key      public int EnquiryId   get  set         Required      public DateTime EnquiryDate   get  set         Required      public string CustomerAccountNumber   get  set         Required      public string ContactName   get  set        I then have a Post action in my API Controller   public void Post Enquiry enquiry        enquiry EnquiryDate   DateTime Now      context DaybookEnquiries Add enquiry       context SaveChanges        How do I add if ModelState IsValid  and then handle the error message to pass down to the user

User · Answer

Or  if you are looking for simple collection of errors for your apps   here is my implementation of this    public override void OnActionExecuting HttpActionContext actionContext                var modelState   actionContext ModelState           if   modelState IsValid                          var errors   new List lt string gt                 foreach  var state in modelState                                foreach  var error in state Value Errors                                        errors Add error ErrorMessage                                                var response   new   errors   errors                 actionContext Response   actionContext Request                  CreateResponse HttpStatusCode BadRequest  response  JsonMediaTypeFormatter DefaultMediaType                     Error Message Response will look like         errors          Please enter a valid phone number  7  more digits         Please enter a valid e-mail address

User · Answer

Add below code in startup cs file  services AddMvc   SetCompatibilityVersion CompatibilityVersion Version 2 2  ConfigureApiBehaviorOptions options   gt                                options InvalidModelStateResponseFactory    context    gt                                        var errors   context ModelState Values SelectMany x   gt  x Errors Select p   gt  new ErrorModel                                               ErrorCode     int HttpStatusCode BadRequest  ToString CultureInfo CurrentCulture                           ErrorMessage   p ErrorMessage                          ServerErrorMessage   string Empty                         ToList                        var result   new BaseResponse                                               Error   errors                          ResponseCode    int HttpStatusCode BadRequest                          ResponseMessage   ResponseMessageConstants VALIDATIONFAIL                                              return new BadRequestObjectResult result

User · Answer

You can also throw exceptions as documented here  http   blogs msdn com b youssefm archive 2012 06 28 error-handling-in-asp-net-webapi aspx  Note  to do what that article suggests  remember to include System Net Http

User · Answer

C       public class ValidateModelAttribute   ActionFilterAttribute               public override void OnActionExecuting HttpActionContext actionContext                        if  actionContext ModelState IsValid    false                                actionContext Response   actionContext Request CreateErrorResponse                      HttpStatusCode BadRequest  actionContext ModelState                                             ValidateModel      public HttpResponseMessage Post  FromBody AnyModel model          Javascript    ajax           type   POST           url    api xxxxx           async   false           contentType   application json  charset utf-8           data  JSON stringify data           error  function  xhr  status  err                if  xhr status    400                    DisplayModelStateErrors xhr responseJSON ModelState                                   function DisplayModelStateErrors modelState        var message           var propStrings   Object keys modelState          each propStrings  function  i  propString            var propErrors   modelState propString             each propErrors  function  j  propError                message    propError                      message      n                alert message

User · Answer

I had an issue implementing the accepted solution pattern where my ModelStateFilter would always return false  and subsequently a 400  for actionContext ModelState IsValid for certain model objects   public class ModelStateFilter   ActionFilterAttribute       public override void OnActionExecuting HttpActionContext actionContext                if   actionContext ModelState IsValid                        actionContext Response   new HttpResponseMessage   StatusCode   HttpStatusCode BadRequest                       I only accept JSON  so I implemented a custom model binder class   public class AddressModelBinder   System Web Http ModelBinding IModelBinder       public bool BindModel HttpActionContext actionContext  System Web Http ModelBinding ModelBindingContext bindingContext                var posted   actionContext Request Content ReadAsStringAsync   Result          AddressDTO address   JsonConvert DeserializeObject lt AddressDTO gt  posted           if  address    null                           moar val here             bindingContext Model   address              return true                    return false            Which I register directly after my model via   config BindParameter typeof AddressDTO   new AddressModelBinder

User · Answer

Like this  for example   public HttpResponseMessage Post Person person        if  ModelState IsValid                PersonDB Add person           return Request CreateResponse HttpStatusCode Created  person             else                  the code below should probably be refactored into a GetModelErrors            method on your BaseApiController or something like that          var errors   new List lt string gt             foreach  var state in ModelState                        foreach  var error in state Value Errors                                errors Add error ErrorMessage                                   return Request CreateResponse HttpStatusCode Forbidden  errors             This will return a response like this  assuming JSON  but same basic principle for XML    HTTP 1 1 400 Bad Request Content-Type  application json  charset utf-8  some headers removed here     A value is required    The field First is required    Some custom errorm essage      You can of course construct your error object list any way you like  for example adding field names  field id s etc   Even if it s a  one way  Ajax call like a POST of a new entity  you should still return something to the caller - something that indicates whether or not the request was successful  Imagine a site where your user will add some info about themselves via an AJAX POST request  What if the information they have tried to entered isn t valid - how will they know if their Save action was successful or not   The best way to do this is using Good Old HTTP Status Codes like 200 OK and so on  That way your JavaScript can properly handle failures using the correct callbacks  error  success etc    Here s a nice tutorial on a more advanced version of this method  using an ActionFilter and jQuery  http   asp net web-api videos getting-started custom-validation

User · Answer

For separation of concern  I would suggest you use action filter for model validation  so you don t need to care much how to do validation in your api controller   using System Net  using System Net Http  using System Web Http Controllers  using System Web Http Filters   namespace System Web Http Filters       public class ValidationActionFilter   ActionFilterAttribute               public override void OnActionExecuting HttpActionContext actionContext                        var modelState   actionContext ModelState               if   modelState IsValid                  actionContext Response   actionContext Request                       CreateErrorResponse HttpStatusCode BadRequest  modelState

User · Answer

Here you can check to show the model state error one by one   public HttpResponseMessage CertificateUpload employeeModel emp                if   ModelState IsValid                        string errordetails                   var errors   new List lt string gt                 foreach  var state in ModelState                                foreach  var error in state Value Errors                                        string p   error ErrorMessage                      errordetails   errordetails   error ErrorMessage                                               Dictionary lt string  object gt  dict   new Dictionary lt string  object gt                    dict Add  error   errordetails               return Request CreateResponse HttpStatusCode BadRequest  dict                       else                   do something

User · Answer

You can use attributes from the System ComponentModel DataAnnotations namespace to set validation rules  Refer Model Validation - By Mike Wasson for details   Also refer video ASP NET Web API  Part 5  Custom Validation - Jon Galloway  Other References   Take a Walk on the Client Side with WebAPI and WebForms How ASP NET Web API binds HTTP messages to domain models  and how to work with media formats in Web API  Dominick Baier - Securing ASP NET Web APIs Hooking AngularJS validation to ASP NET Web API Validation Displaying ModelState Errors with AngularJS in ASP NET MVC How to render errors to client  AngularJS WebApi ModelState Dependency-Injected Validation in Web API

User · Answer

Maybe not what you were looking for  but perhaps nice for someone to know   If you are using  net Web Api 2 you could just do the following   if   ModelState IsValid       return BadRequest ModelState     Depending on the model errors  you get this result        Message   The request is invalid      ModelState           model PropertyA                 The PropertyA field is required                    model PropertyB                  The PropertyB field is required

[c#] Handle ModelState Validation in ASP.NET Web API

Examples related to c#

Examples related to asp.net-web-api