Question

I’m getting an exception that the JSON request was too large to be deserialized.

It’s coming from the JsonValueProviderFactory….

The MVC App currently has a custom model binder using Json.Net which has no problem deserializing the json data. However I’m assuming the default JSON value provider is tripping up? or has some weird limit built into it?

It may be be to do with the latest release of MVC4 as when using the previous build of MVC4 there were no problems with large amounts of JSON.

So, is there a way to change the setting s of the actual json value binder?

going by http://haacked.com/archive/2011/06/30/whatrsquos-the-difference-between-a-value-provider-and-model-binder.aspx

I get the impression it’s some custom thing that turns it into a dictionary….I can’t find any source code related to it or if there are any settings I can change?

Or is there an alternative ValueBinder I could use?

or any other options?

Server Error in '/' Application.
The JSON request was too large to be deserialized.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: The JSON request was too large to be deserialized.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[InvalidOperationException: The JSON request was too large to be deserialized.]
   System.Web.Mvc.EntryLimitedDictionary.Add(String key, Object value) +464621
   System.Web.Mvc.JsonValueProviderFactory.AddToBackingStore(EntryLimitedDictionary backingStore, String prefix, Object value) +413
   System.Web.Mvc.JsonValueProviderFactory.AddToBackingStore(EntryLimitedDictionary backingStore, String prefix, Object value) +164
   System.Web.Mvc.JsonValueProviderFactory.AddToBackingStore(EntryLimitedDictionary backingStore, String prefix, Object value) +164
   System.Web.Mvc.JsonValueProviderFactory.AddToBackingStore(EntryLimitedDictionary backingStore, String prefix, Object value) +373
   System.Web.Mvc.JsonValueProviderFactory.AddToBackingStore(EntryLimitedDictionary backingStore, String prefix, Object value) +164
   System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext controllerContext) +116
   System.Web.Mvc.<>c__DisplayClassc.<GetValueProvider>b__7(ValueProviderFactory factory) +34

       System.Linq.WhereSelectEnumerableIterator`2.MoveNext() +151
   System.Linq.WhereSelectEnumerableIterator`2.MoveNext() +177

Answer 1

If you use JSON.NET for serialization/deserialization, you could substitute the default JsonValueProviderFactory with a custom one as shown in this blog post:

public sealed class JsonDotNetValueProviderFactory : ValueProviderFactory
{
   public override IValueProvider GetValueProvider(ControllerContext controllerContext)
   {
        if (controllerContext == null)
            throw new ArgumentNullException("controllerContext");

        if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
            return null;

        var reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
        var bodyText = reader.ReadToEnd();

        return String.IsNullOrEmpty(bodyText) ? null : new DictionaryValueProvider<object>(JsonConvert.DeserializeObject<ExpandoObject>(bodyText, new ExpandoObjectConverter()) , CultureInfo.CurrentCulture);
    }
}

and in your Application_Start:

ValueProviderFactories.Factories.Remove(ValueProviderFactories.Factories.OfType<JsonValueProviderFactory>().FirstOrDefault());
ValueProviderFactories.Factories.Add(new JsonDotNetValueProviderFactory());

and if you want to stick with the default factory which uses the JavaScriptSerializer class you could adjust the maxJsonLength property in your web.config:

<system.web.extensions>
    <scripting>
        <webServices>
            <jsonSerialization maxJsonLength="2147483644"/>
        </webServices>
    </scripting>
</system.web.extensions>