Try this
public override void OnActionExecuting(HttpActionContext context)
{
var modelState = context.ModelState;
if (!modelState.IsValid)
{
var errors = new JObject();
foreach (var key in modelState.Keys)
{
var state = modelState[key];
if (state.Errors.Any())
{
errors[key] = state.Errors.First().ErrorMessage;
}
}
context.Response = context.Request.CreateResponse<JObject>(HttpStatusCode.BadRequest, errors);
}
}
From the client ajax request, on error, get the responseText to process the validation error messages.
You might want to pick a HttpStatusCode based on what you are trying to do, since the