Accessing the Current Principal in VSTO Add-In

I recently tried to get access to the Current Principal within an Outlook Add-In. Accessing the Identity was returning a blank name and an unauthorised user. Wierd.

It turns out the the VSTOLoader will load each Add-In into its own AppDomain. As such, you need to set the principal policy explicitly before you access the current principal for the first time.

Example:

AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
string userName = Thread.CurrentPrincipal.Identity.Name;

As it running within an isolated environment, I am sure there are other issues you need to be aware of.

See the AppDomain Class in the MSDN Library for more information on application domains.