Business Portal Customization

Dear All, 

i am trying to do a small customization on business portal 

i have found this white paper helpful in this matter ,

Using Web Services in Business Portal

 http://www.microsoft.com/en-us/download/details.aspx?displaylang=en&id=22249

when ever i try the code attached , to create the functionality descried in the white paper 

it is given me the following error message 

The Microsoft Business Framework must be started using EnterpriseSession.Initialize().

which is related to these lines

using Microsoft.BusinessFramework
using Microsoft.BusinessFramework.Entity;

//Method to use company database ID from BP session

public int GetDBID()
{
int dbID;
EntityKey eK;

eK = (Microsoft.Dynamics.Common.Company.Company.Key)EnterpriseSession.DefaultParentKey;

Microsoft.Dynamics.Common.Company.Company company = (Microsoft.Dynamics.Common.Company.Company)eK.GetEntity();

dbID = company.ID;

return dbID;
}

am i doing some thing wrong , or what

any help will be very thankful