Custom JSON Model Binder for deserialization with Newtonsoft JSON in ASP.NET MVC 5

Question

I wrote this to have ASP.NET MVC be able to respond as a web API as well as the normal MVC Razor pages. I wanted Newtonsoft deserialization for models based on already parsed values:

public class CustomJsonModelBinder<T> : DefaultModelBinder
 where T : class
{
 public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
 {
 if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
 {
 return base.BindModel(controllerContext, bindingContext);
 }
 if (bindingContext.ModelType != typeof(T))
 {
 return base.BindModel(controllerContext, bindingContext);
 }
 //Get the DictionaryValueProvider, the one with all the JSON values already read
 if (!(bindingContext.ValueProvider is ValueProviderCollection valueProviders))
 {
 return base.BindModel(controllerContext, bindingContext);
 }
 DictionaryValueProvider<object> dictionaryValueProvider = valueProviders.FirstOrDefault(x => x.GetType() == typeof(DictionaryValueProvider<object>)) as DictionaryValueProvider<object>;
 if (dictionaryValueProvider == null)
 {
 return base.BindModel(controllerContext, bindingContext);
 }
 /* get the values and build a temp object for them for proper Newtonsoft Deserialization, which can have formatting attributes and others on the target class */
 Dictionary<string, object> valueDictionary = new Dictionary<string, object>();
 foreach (var entry in dictionaryValueProvider.GetKeysFromPrefix(""))
 {
 var value = bindingContext.ValueProvider.GetValue(entry.Key);
 valueDictionary.Add(entry.Key, value.RawValue);
 }
 string dictionaryInJson = JsonConvert.SerializeObject(valueDictionary);
 return string.IsNullOrEmpty(dictionaryInJson) ? base.BindModel(controllerContext, bindingContext) : JsonConvert.DeserializeObject<T>(dictionaryInJson);
 }
}

Usage:

public ActionResult Post(int id,[ModelBinder(typeof(CustomJsonModelBinder<AppointmentRequest>))] AppointmentRequest model)

I don't like having to repeat the model type twice, but I see no other convenient way.

Please let me know your thoughts!

• iSR5: implement IModelBinderProvider to get rid of the ModelBinder attribute. read more
• infinitezero: Just curious why you chose NewtonSoft over the built-in?
• MPelletier: @infinitezero First off, we ended up not going this route but instead using Web API 2.0 (with a "right tool for the right job" kinda-philosophy). My rationale was to use Newtonsoft instead of the built-in library which happens to be JavaScriptSerializer. It is not as customizable as Newtonsoft.
• infinitezero: I don't know how it compares to Newtonsoft but the correct built-in is JsonSerializer. JavascriptSerializer is obsolete
• MPelletier: @infinitezero Are you thinking of MVC Core? This was for MVC 5.