The code below causes a red squiggle even though it compiles fine. The lack of the where-condition in the concrete class seems to confuse Resharper, and the where-condition from the interface does not seem to be passed through. using System; using System.Collections; using System.Collections.Generic; public interface IItem { int Id { get; } } public interface IMyInterface { void DoThis<TItem>(TItem item) where TItem : IItem; } public abstract class MyInterfaceBase : IMyInterface { public abstract void DoThis<TItem>(TItem item) where TItem : IItem; } public class OneImplementation : MyInterfaceBase { public override void DoThis<TItem>(TItem item) { int x = item.Id; } }