Hi Steven,
if yours is an ASP.NET 2.0 application you can use the ASP.NET 2.0 security model to access AzMan indirectly thru its provider model (you can read about that here: http://msdn2.microsoft.com/en-us/architecture/ms998336.aspx)
If your application, being web or not, needs to access an AzMan repository from a non-web environment, you can leverage the EnterpriseLibrary 2.0 Security application block, which uses a similar principle like ASP.NET 2.0 (more info here: http://msdn2.microsoft.com/en-us/architecture/aa480465.aspx)
Hope you can stop developing your own API and focus in application logic 
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