public static class OrderIndex
{
    public abstract class Order { }

    public abstract class Order1 : Order { }

    public abstract class Order2 : Order { }

    public abstract class Order3 : Order { }

    public abstract class Order4 : Order { }
}

public class Condition<T>
{
}

public class FooCondition<T> : Condition<T>
    where T : OrderIndex.Order
{
    ...
}

public class BarCondition<T> : Condition<T>
    where T : OrderIndex.Order
{
    ...
}

public class BazCondition<T> : Condition<T>
    where T : OrderIndex.Order
{
    public BazCondition(FooCondition<T> foo, BarCondition<T> bar)
    {
        ...
    }
}