If The first item in the comparison cannot be cast to an IStructuralEquatable object (in other words, if it is derece a collection object that implements the IStructuralEquatable interface), it calls the item's Equals method. But, needless to input StructruralEqualityComparer because int is not structural, you should just use: C# https://c-object-kullan-m29516.birderswiki.com/772854/büyülenme_hakkında_c_structuralcomparisons_nedir