I'm using Umbraco 7.4.2 and went through this article to setup Autofac into my solution but after setting it all up, I noticed the backoffice started throwing errors.

My code for registering my components:

public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
{
    var builder = new ContainerBuilder();

    //register all controllers found in this assembly
    builder.RegisterControllers(Assembly.GetExecutingAssembly());

    //register umbraco webapi controllers used by the admin site
    builder.RegisterApiControllers(typeof(UmbracoApplication).Assembly);

    var container = builder.Build();
    DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
    GlobalConfiguration.Configuration.DependencyResolver = new AutofacWebApiDependencyResolver(container);
}

And the error I'm getting from the backoffice on this call - /umbraco/backoffice/UmbracoTrees/ApplicationTree/GetApplicationTrees?application=users&tree=&isDialog=false:

"Message":"An error has occurred.",
"ExceptionMessage":"Object reference not set to an instance of an object.",
"ExceptionType":"System.NullReferenceException",
"StackTrace":"   at Umbraco.Web.WebApi.Filters.DisableBrowserCacheAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
   at System.Web.Http.Filters.ActionFilterAttribute.OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken)
   --- End of stack trace from previous location where exception was thrown ---
      at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
      at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
         at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
         --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
               at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
               at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
                     at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
                     --- End of stack trace from previous location where exception was thrown ---
                        at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
                     --- End of stack trace from previous location where exception was thrown ---
                        at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                           at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
                              at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
                              --- End of stack trace from previous location where exception was thrown ---
                                 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                                    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
                                       at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
                                       --- End of stack trace from previous location where exception was thrown ---
                                          at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                                             at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
                                                at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()
                                                --- End of stack trace from previous location where exception was thrown ---
                                                   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                                                      at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
                                                      at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()""

Did some debugging and found commenting this line solves the backoffice issue:

DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

But then I can't use DI for my controllers.

Thoughts anyone? Thanks in advance.