WordPress Remote POST login from .Net site

Hi,

I attempting to perform an HttpWebRequest from an existing ASP.Net website. We will be retiring the .Net site in the coming months but there is a requirement to run the two sites side by side and there is functionality that should be available to certain users etc. hence the need for cross authentication. I have found various articles on creating in effect a SSO for WordPress but have not had any joy implementing them, this is the main one:

http://stackoverflow.com/questions/4411397/asp-net-to-wordpress-sso-with-httpwebrequest

I get the wordpress_logged_in_XXXXXXXXXXX cookie but nothing else and I’m still required to login if I visit the restricted pages of the WordPress instance. I wondered if anyone has any experience of this and whether I am going about it the right way. I have looked for some form of api but I cannot find anything of use.