You can achieve that by creating non-generic base classes for the generic base classes. Answer updated to avoid type casting.

You can achieve that by creating non-generic base classes for the generic base classes. Answer updated to avoid type casting; to do so, ChildObjects property had to be IEnumerable<T> because it's type parameter is covariant, while classes, IList<T>, and ICollection<T> are contravariant.

You can achieve that by creating non-generic base classes for the generic base classes.

public abstract class ManagerBase { public List<ChildBase> ChildObjects { get; set; } } public abstract class Manager<T> : ManagerBase where T : ChildBase { public Manager() { ChildObjects = new List<T>(); } public new List<T> ChildObjects  { get { return base.ChildObjects.Cast<T>().ToList(); } set { base.ChildObjects = value.ToList<ChildBase>(); } } } public abstract class ChildBase { public ManagerBase ParentMgr { get; set; } } public abstract class Child<T> : ChildBase where T : ManagerBase { public Child(T parentMgr) { ParentMgr = parentMgr; ParentMgr.ChildObjects.Add(this); } public new T ParentMgr { get { return (T)base.ParentMgr; } set { base.ParentMgr = value; } } } 

You can achieve that by creating non-generic base classes for the generic base classes. Answer updated to avoid type casting.

public abstract class ManagerBase { protected ManagerBase()    {    innerChildObjectList = new List<ChildBase>();  }  private IList innerChildObjectList; public IEnumerable<ChildBase> ChildObjects   {  get { foreach (ChildBase child in innerChildObjectList.OfType<ChildBase>()) yield return child; }  }  public void AddChild<T>(T child) where T : ChildBase  {  innerChildObjectList.Add(child); } public void RemoveChild<T>(T child) where T : ChildBase { innerChildObjectList.Remove(child); } public bool ContainsChild<T>(T child) where T : ChildBase {    return innerChildObjectList.Contains(child);  } //Add 'Insert', 'RemoveAt' methods if needed. } public abstract class Manager<T> : ManagerBase  where T : ChildBase {    public new IEnumerable<T> ChildObjects    { get { return base.ChildObjects.OfType<T>(); } } } public abstract class ChildBase { protected ChildBase(ManagerBase mgr)  {    ParentMgr = mgr;  } private ManagerBase parentMgr;  public ManagerBase ParentMgr   {  get { return parentMgr; }  set  {  if (parentMgr != null && parentMgr.ContainsChild(this))  parentMgr.RemoveChild(this);   parentMgr = value;  parentMgr.AddChild(this);   } } } public abstract class Child<T>  : ChildBase where T : ManagerBase { protected Child(T mgr) : base (mgr) { } public new T ParentMgr { get { return base.ParentMgr as T; } set { base.ParentMgr = value; } } }