Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.

When trying to return a large dataset, perhaps an array of items using JSON from both a web service or a controller, you might run into the Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property. error.

This is a simple fix for both Web Services and MVC Controllers alike, check below for the fix to both setups.

Increase maxJsonLength in Web Service

Update your web.config with the following:

<configuration> 
   <system.web.extensions>
       <scripting>
           <webServices>
               <jsonSerialization maxJsonLength="50000000"/>
           </webServices>
       </scripting>
   </system.web.extensions>
</configuration> 

Increase maxJsonLength in MVC Controller

Place this within your controller.

protected override JsonResult Json(object data, string contentType, System.Text.Encoding contentEncoding, JsonRequestBehavior behavior)
{
    return new JsonResult()
    {
        Data = data,
        ContentType = contentType,
        ContentEncoding = contentEncoding,
        JsonRequestBehavior = behavior,
        MaxJsonLength = Int32.MaxValue
    };
}