c# - Modelling a business hierarchy -

I have a dashboard application where the user can navigate up and down through the 'Business Unit' hierarchy and its Can see data for unit

The hierarchy is as follows:

  Company | | Office Department Group | | Department | Stream | Employee   
 How can I model this object using the object I think is that I will have an IETIT interface like:  
  Public Interface IERTIT {Int entity {get} Set; } String EntityCode {get; Set; } String EntityName {get; Set; } List & lt; IEntity & gt; Children {receive; Set; } List & lt; IEntity & gt; Parents {receive; Set; }}   
 How should I model my concrete sections to implement this structure?   
 
 
 My concern here would be to remove the benefits of referring to a solid type list in the context of IRETTE will be given. If a department can only be in the sections, then I will have a property that is a  IList & lt; Department & gt;  (or  IList & lt; idPember & gt;  if you are Commitment-Shy)  IList & lt; IEntity & gt; ) that are not worth the flexibility of the required flexibility.