title: RegisterInstance can't register with IntstancePerRequestMode in Autofac
body: <p>I have a code in Web Api Delegating Handler that extract data from request header.
  However,  I can't register instance in Autofac container because Autofac container require SingleInstance only.</p>
  
  <pre><code>            public class ExtractUserNameMessageHandler : DelegatingHandler
  {
      protected async override Task&lt;HttpResponseMessage&gt; SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  var userNameFromFrontEnd = request.GetDependencyScope().GetService(typeof (IUserNameFromFrontEnd));
          if (userNameFromFrontEnd == null)
          {
              var updatedContainerBuilder = new ContainerBuilder();
              userNameFromFrontEnd = ExtractUserName(request);
              if (userNameFromFrontEnd == null)
              {
                  throw new Exception("We've got a request without UserName header");
              }
              updatedContainerBuilder.RegisterInstance(userNameFromFrontEnd)
                  .As&lt;IUserNameFromFrontEnd&gt;()
                  .InstancePerRequest();
              var autofacDependencyResolver = GlobalConfiguration.Configuration.DependencyResolver as AutofacWebApiDependencyResolver;
              if (autofacDependencyResolver == null)
              {
                  throw new Exception("We can work with Autofac DI container");
              }
              updatedContainerBuilder.Update(autofacDependencyResolver.Container as IContainer);
          }
  </code></pre>
  
  <p>When I try to update container I get an exception with message -  registration can support singleinstance() sharing only.</p>
  
  <p>What does it mean? I can't understand why we have this limitation. But in any cases my first goal - update container with new dependency. 
  Does anybody have ideas?</p>