ASP.NET Web Api Validation with Data Annotations

I’ve recently moved a project over Web Api over to ASP.NET Web Api. In doing that I needed to re-implement my validation code. Thanks to the Api being a part of the MVC framework, things are much simpler now.

 Previously I was Explained About  Difference between WCF and Web API and WCF REST and Web Service ,  Repeater Vs. DataList vs. ListView Vs. GridView , IEnumerable VS IQueryable

public class ValidationActionFilter : ActionFilterAttribute {     public override void OnActionExecuting(HttpActionContext context)     {         var modelState = context.ModelState;         if (!modelState.IsValid)         {             dynamic errors = new JsonObject();             foreach (var key in modelState.Keys)             {                 var state = modelState[key];                 if (state.Errors.Any())                 {                     errors[key] = state.Errors.First().ErrorMessage;                 }             }             context.Response = new HttpResponseMessage<JsonValue>(                 errors,                 HttpStatusCode.BadRequest);         }     } }

All I need do now is decorate my models appropriately, for example …

public class TellAFriend {     [StringLength(100)]     public string ToName { get; set; }     [StringLength(100)]     [Required]     [RegularExpression(Regexes.EmailPattern, ErrorMessage = "Invalid email address")]     public string ToEmailAddress { get; set; } }

I will get a HTTP 400 response with a nice array of key/value pairs in the response body whenever a client sends me bad data.

{     "ToEmailAddress": "Invalid email address" } Source From :  http://www.asp.net/web-api/overview/formats-and-model-binding/model-validation-in-aspnet-web-api http://www.dotnetcurry.com/ShowArticle.aspx?ID=927 http://msdn.microsoft.com/en-us/magazine/dn201742.aspx