Allow anonymous access to SharePoint application pages in the _layouts directory

 

By default, the page is inherited from “LayoutsPageBase”. Change the inheritance
from “LayoutsPageBase” to “UnsecuredLayoutsPageBase”. 

public partial class HelloWorld : UnsecuredLayoutsPageBase

Next, we need to override a property of the UnsecuredLayoutsPageBase, to allow the
anonymous access. Be sure to change the ‘getter’ to return true 

protected override bool AllowAnonymousAccess { get { return true; } }