title: Having IApplicationBuilder in .NET Framework
body: <p>I apologize if this isn't architecturally possible,
  but I'm just trying to integrate certain .NET Core features
  into my existing old Webforms application, as I would someday like
  to move to .NET Core, but I don't want to continue writing
  outdated code.</p>
  
  <p>Anyways, when using <code>Microsoft.Owin.Host.SystemWeb</code>
  my application requires a Startup Class.
  However it expects a method: <code>Configuration(IAppBuilder app)</code>,
  but the features I am looking for (e.g. <code>app.UseMvc()</code>) require
  <code>app</code> to be of <code>IApplicationBuilder</code>.</p>
  
  <p>Could one to hackishly convert a <code>IAppBuilder</code> to <code>IApplicationBuilder</code>?
  I'd imagine if such a thing were possible,
  it would require bringing in a few other classes.</p>
  
  <p>Or even better, is there a Package similair to <code>SystemWeb</code> that looks for
  a Startup class but instead expects <code>Configure(Iapplicationbuilder app, ...)</code>.</p>
  
  <p>It seems somewhat outlandish, but it would be nice to be able to do,
  and if anyone knows how to do such a thing, it would be here.</p>