Specifies whether authentication is valid for a single request if by proxy. IIS will reset the authentication at the end of the request and force re-authentication on the next request if the current authenticated request is by proxy of any type. Applies to IIS 5.0 and 5.1. The default is false.

[TaskAttribute("authpersistsinglerequestalwaysifproxy"), IisProperty]
public bool AuthPersistSingleRequestAlwaysIfProxy { get; set; }