It's Normally expected that if you implement IEquatable.Equals you will also override Object.Equals to be consistent. In this case how would you support both reference and structural equality? The IEqualityComparer from input parameter is used, in here you input StructruralEqualityComparer but int does derece implement IStructruralEquatable, so it uses default https://alexistfmta.dekaronwiki.com/814973/en_c_structuralcomparisons_temel_Özellikleri_sırları