Solution: The length of the string exceeds the value set on the maxJsonLength property for POST action

Question

I've following code in MVC. In my POST action params will have huge data. So, I changed web.config accordingly but, I'm getting ERROR. Actual problem is controller is not even hitting when POST is called.

I tried Following ways

1. Override JsonResult
2. followed Link. Here i couldn't see data which is sent from script. I'm getting NULL in base64.

controller.cs

 [System.Web.Mvc.HttpPost]
    public bool postImage(string base64)
    {
       return true;
    }

web.config

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

JavaScript

  $.ajax({
  type: "POST",
  url: 'http://localhost:21923/communities/postImage?base64=',
  contentType: "application/json; charset=utf-8",
  data: JSON.stringify(data),
  dataType: "json",
  success: function(data) {
    document.getElementById('test').click();
  },
  error: function(a, b, c) {
    console.log(a);
  }
})

Error

Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.\r\nParameter name: input

Answer 1

Create a JsonDotNetValueProviderFactory.csand write following code:

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 add following two lines in Global.asax.cs in Application_Start()

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

Source: Link

Thanks to Darin Dimitrov !!

If above code fails: Follow This might helps a lot

Thanks to dkinchen !!