System.InvalidOperationException: Collection was modified; enumeration operation may not execute. at System.Collections.Generic.HashSet`1.Enumerator.MoveNext() at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext() at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source) at Smartpage.Nav.MainItem.Providers.ProductProvider.GetProductMainItems(ICollection`1 products) in c:\Workspace\55 nord\Main\Source\55Nord.MainItem\Providers\ProductProvider.cs:line 139 at Smartpage.Nav.MainItem.Providers.ProductProvider.GetProductMainItems(Product product) in c:\Workspace\55 nord\Main\Source\55Nord.MainItem\Providers\ProductProvider.cs:line 56 at Smartpage.Nav.MainItem.TemplateExtenders.ProductTemplateExtender.ExtendTemplate(Template template) in c:\Workspace\55 nord\Main\Source\55Nord.MainItem\TemplateExtenders\ProductTemplateExtender.cs:line 13 at Dynamicweb.eCommerce.Frontend.Renderer.RenderProductTemplateExtenders(Product Product, Template Template, Boolean ExtendedProperties) at Dynamicweb.eCommerce.Frontend.Renderer.RenderProduct(Product Product, Boolean ExtendedProperties, Template Template, Int32 loopCounter, Boolean renderRelated, String productURL, Int32 quantity, Int32 wishListID, Boolean renderPublicList, Int32 orderLineOfProductCount) at Dynamicweb.eCommerce.Frontend.Renderer.RenderProducts(ProductCollection Products, Template ParentTemplate, String LoopName, Int32 LoopCounter, Boolean renderRelatedProducts, Boolean renderRelatedLists) at Dynamicweb.eCommerce.Frontend.Renderer.RenderProducts(ProductCollection Products, Template ParentTemplate) at Dynamicweb.eCommerce.Frontend.Renderer.internalRenderProducts(ProductCollection products, Boolean isProductsFromIndex) at Dynamicweb.eCommerce.Frontend.Frontend.ListProducts(ProductCollection products, String groupsIdent, Boolean hasBeenSorted) at Dynamicweb.eCommerce.Frontend.Frontend.GetProductsFromIndexQuery()