title: Use FormsAuthentication.SignOut() in ASMX web service
body: <p>I have a web service, let's say User.asmx and it has a method LogoutUser().</p>
  
  <p>Service is consumed by an external website and what I want to do is when user log out from that external website, they will make a call to our service to log out user from my website as well. This is required when user logs into my site he gets redirected to that external website.</p>
  
  <p>Any ideas how would I be able to do it? FormsAuthentication.SignOut() seems to work locally or on my test machine but when client tries to call the service, user doesn't get log out. We cannot avoid using cookie for forms authentication in our website.</p>
  
  <p>Thanks in advance.</p>