The offline examples shipped along with the ASP.NET MVC wrappers should work without any modifications, so I am really not sure why you are getting an error. Could you please share more details, for example the exact error message? You can also check if the file containing the productService class exists. It should be located here:
Kendo UI installation path\wrappers\aspnetmvc\Examples\VS2012\Kendo.Mvc.Examples\Models\ProductService.cs
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