Most published WebAPI samples (e.g. http://msdn.microsoft.com/en-us/library/azure/dn646737.aspx) are based on the MVC and OWin infrastructure, which is not available in WebForms applications. Following is a custom implementation of an OAuth2 access token handler presented by a WPF rich client application. The WPF is responsible for managing the OAuth code grant flow to obtain the token and present it to the WebForms application as part of an HTTP call. The code is based on the above samples but modified to support WebForms.