Exception information:
Exception type: InvalidOperationException
Exception message: Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.
Solution
<configuration>
<system.web.extensions>
<scripting>
<webServices>
<jsonSerialization maxJsonLength="50000000"/>
</webServices>
</scripting>
</system.web.extensions>
</configuration>