How to decode and cast JSON string in Flex?

You need to do something similar to what this page says: http://benrimbey.wordpress.com/2009/06/20/reflection-based-json-validation-with-vo-structs/

The problem with your code is you are trying to downcast a native Object into a specific Class instance that it knows nothing about. The structures of your two types are different. UserInfo inherits from Object (in a sort of funky AS3 way because of the way Classes are compiled), but b is a simple Object.

FYI if you are just doing JSON decoding, and it is a Flex app, not AIR. You do not need the as3Corelib package to do so. You can just use the parent browser's JavaScript interpreter like this:

var myJSONString:String = "{name:'Joe',age:35}";var myObj:Object = ExternalInterface.call('eval', "("+myJSONString+")");

This might save your user a few Kb on the download.

Glenn's link really did the trick. I also added a conversion between dot-net and AS3 - it seems that dot-net writes the __type attribute like so: "Class:Namespace", but AS3 needs it to be like so: "Namespace.Class".

private static function convertDotNetToASNameType(nameType:String):String            {    return(nameType.split(':').reverse().join('.'));}

BTW, if you are using Glenn's link and a WCF server, be sure to replace "clientClassPath" with dot-net's "__type".