I have developed a custom membership provider (say, with the name TestMemProvider) and have registered the same in the 3 web.config files for SharePoint in a Forms Claims based web application with multitenant site collections. Now, when I am trying to access the MembershipProvider object in an application page within a SharePoint site using the following line, I am getting mp as null. Can anyone please help?
MembershipProvider mp = Membership.Providers["TestMemProvider"]
Ven