using System;

namespace Eg.Core
{
public abstract class Entity
    {

public virtual TId Id { get; protected set; }
protected virtual int Version { get; set; }

public override bool Equals(object obj)
        {
return Equals(obj as Entity);
        }

private static bool IsTransient(Entity obj)
        {
return obj != null &&
                   Equals(obj.Id,default(TId));
        }

private Type GetUnproxiedType()
        {
return GetType();
        }

public virtual bool Equals(Entity other)
        {
if (other == null)
return false;

if (ReferenceEquals(this, other))
return true;

if (!IsTransient(this) &&
                !IsTransient(other) &&
                Equals(Id, other.Id))
            {
var otherType = other.GetUnproxiedType();
var thisType = GetUnproxiedType();
return thisType.IsAssignableFrom(otherType) ||
                       otherType.IsAssignableFrom(thisType);
            }

return false;
        }

public override int GetHashCode()
        {
if (Equals(Id, default(TId)))
return base.GetHashCode();
return Id.GetHashCode();
        }

    }

public abstract class Entity : Entity
    {

    }

}