Crystal Reports :: Authenticate Website Service Methods Using Soap Header

I am trying to implement webservice authentication using SOAP Header. how to provice single authentication which applied to all the methoads of webservice.

Example : 

public class Service:System.Web.Services.WebService
{
public AuthSoapHd spAuthenticationHeader;

public Service()

[code]....

On this sample it has only one method and based on the username and password mataches it provides  access. As like this there are plenty of web methoad's in my webservice and i don't want to check the username and password on all the methoads. instead i wanted to checkonce and provide access to all the methods.