title: How do you create a custom AuthorizeAttribute in ASP.NET Core?
body: <p>I'm trying to make a custom authorization attribute in ASP.NET Core.  In previous versions it was possible to override <code>bool AuthorizeCore(HttpContextBase httpContext)</code>.  But this no longer exists in <a href="https://github.com/aspnet/Security/blob/3a8ea672eae590785a78d74777abb76bb9664130/src/Microsoft.AspNet.Authorization/AuthorizeAttribute.cs"><code>AuthorizeAttribute</code></a>.</p>
  
  <p>What is the current approach to make a custom AuthorizeAttribute?</p>
  
  <p>What I am trying to accomplish: I am receiving a session ID in the Header Authorization. From that ID I'll know whether a particular action is valid.</p>