Hi, Whats is the correct way to cancel a content coping event? I have in my ApplicationStarted event

    protected override void ApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        ContentService.Copying += ContentService_Copying;
    }

and my ContentService_Copying method:

        private void ContentService_Copying(IContentService sender, CopyEventArgs<IContent> e)
    {
        e.CancelOperation(new EventMessage("", "You can not copy", EventMessageType.Error));
    }

If i run the above i then get an error in the backend:

System.NullReferenceException: Object reference not set to an instance of an object. Stacktrace

at Umbraco.Web.Editors.ContentController.PostCopy(MoveOrCopy copy)

at lambda_method(Closure , Object , Object[] )

at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>cDisplayClass10.9(Object instance, Object[] methodParameters)

at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)

at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, 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.Controllers.ApiControllerActionInvoker.

--- 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.

--- End of stack trace from previous location where exception was thrown ---

at System.Web.Http.Filters.ActionFilterAttribute.

--- 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.

--- 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.

--- End of stack trace from previous location where exception was thrown ---

at System.Web.Http.Filters.ActionFilterAttribute.

--- 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.

--- 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.

--- End of stack trace from previous location where exception was thrown ---

at System.Web.Http.Filters.ActionFilterAttribute.

--- 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.

--- 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.

--- End of stack trace from previous location where exception was thrown ---

at System.Web.Http.Filters.ActionFilterAttribute.

--- 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.

--- 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.

--- End of stack trace from previous location where exception was thrown ---

at System.Web.Http.Filters.ActionFilterAttribute.

--- 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.

--- 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.

--- 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.

--- 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.

--- 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.

--- 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.

So it looks like the event does get cancelled but i end up with a null reference. So the question is i guess is how do i stop this error bubbling up to the back end UI and replace it with a nicer message? Any ideads anyone?

cheers,

Mark