JavaScriptSerializer Error when i am using it in Sharepoint Project

hi,

I am getting an error when i am using the JavascriptSerializer method in sharepoint  project.

below is the code and error 

// get the web response
        string result = RequestHandler.Process(apiURL);

        // serialize the json output and parse in the helper class
        LocalWeather Weather = (LocalWeather)new JavaScriptSerializer().Deserialize(result, typeof(LocalWeather));

        return Weather;

Error:  No overload for method 'Deserialize' takes 2 arguments

but it is working in Website project , i am getting no error.

Thanks

sal