How to Get value from ienumerable list?

Question

Hi,

I tried

var maxId = HouseList.Max(h => h.HouseId);

but i get error as

Sequence contains no elements

But I had loaded element into list as

 public void LoadHouse()
        {
            _stx = new CPMDomainContext();
            LoadOperation<House> lo = _stx.Load(_stx.GetHousesQuery());
            HouseList = lo.Entities;
        }

I use HouseList as ItemSource for a combobox..It binds data..But while i check HouseList.count always zero.How can i get elements from HouseList.Help me..