Profile: umut.gulkok

My site (v2.50) is a book store site. It and the ajax filters were funtioning well. However, I had to add a new table for book authors, this table's relationship with the products is exactly the sama as the manufacturers.

After some work some methods in the IProductService changed like the following
IPagedList<ProductVariant> SearchProductVariantsEx(int categoryId, int manufacturerId, string keywords, bool searchDescriptions, int pageIndex, int pageSize, bool showHidden = false, int writerId = 0);

This bold writerId parameter is added. But since it is optional it shouldn't be a problem.

I get the below exception when I click some specification in the ajax filter while the jquery post a command to "http://localhost:2640/Catalog7Spikes/GetFilteredProducts"

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Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

[MissingMethodException: No parameterless constructor defined for this object.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +69
   System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +67
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I gues this exception is very tipical when there is an inconstistency between nop services and sevenspikes core. But in order to correct the problem I should know all the dependencies between them. Which interfaces/services are critical for the sevenspikes core and ajax filter?