Unable to fetching image in browser to window phone application

Question

Hi, I am trying to retrieve the image from the browser using WCF and window phone application. http://debugmode.net/2010/04/27/picture-gallery-for-windows-7-phone-using-wcf-rest-service/#comment-5492 The link is the reference what I am doing. I manage to do all the step it state in the link but I have an error on 

DataContractSerializer ds = new DataContractSerializer(typeof(List<string>));

The error state that The type of namespace name 'DataContractSerializer' Could not be found. If I generate class on it, I will get another error which 'RESTServiceConsuming.DataContractSerializer' does not contain a constructor that takes 1 arguments. The ReadObject will be no definition and no extension method 'ReadObject' accepting a first argument of type 'RESTServiceConsuming.DataContractSerializer' could be found(are you missing a using directive or an assembly reference?)


I just change the interface from combo box to list box because visuo studio 2010 do not have combo box feature. May anyone expert can help me? I am new to it and I really need it to do for my final year project. Here I attach the error example for after generate class and before generate class.Thank you.