There is a 54-reply long thread here on the subject - https://our.umbraco.com/forum/umbraco-forms/87608-multi-page-form-save-data - but this covers Umbraco 7 & 8 mostly, so I thought I'd created a separate thread for v9 chat on the topic.

I was hoping that this would be a little easier in v9, with events being handled by Notifications, but I've hooked up all the Forms notifications to handlers and as far as I can tell, moving between pages isn't something that's supported by a Notification.

If you're interested in what all the Forms notifications here, I've put the code at the bottom of this post to save you some time finding them.

All I want to do is:

• Logged in Member opens a Form
• Member completes a page and clicks to move to the next page
• Progress is saved against this member record (repeat for each page)
• Member leaves the site for an unspecified amount of time
• Member returns, opens the form and their state is restored
• Member completes and submits the form

Is the method outlined in the thread above still the way to do it? Replacing the whole Forms Surface Controller seems like a sledgehammer approach for this.

I'm hoping someone has a better method for v9.

Here's the Notification code...

using Umbraco.Cms.Core.Events;
using Umbraco.Forms.Core.Services.Notifications;

namespace My.Notifications
{
    public class DataSourceSavingNotificationHandler : INotificationHandler<DataSourceSavingNotification>
    {
        public void Handle(DataSourceSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class FolderCreatedNotificationHandler : INotificationHandler<FolderCreatedNotification>
    {
        public void Handle(FolderCreatedNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class FolderCreatingNotificationHandler : INotificationHandler<FolderCreatingNotification>
    {
        public void Handle(FolderCreatingNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class FolderDeletedNotificationHandler : INotificationHandler<FolderDeletedNotification>
    {
        public void Handle(FolderDeletedNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class FolderDeletingNotificationHandler : INotificationHandler<FolderDeletingNotification>
    {
        public void Handle(FolderDeletingNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class FolderSavedNotificationHandler : INotificationHandler<FolderSavedNotification>
    {
        public void Handle(FolderSavedNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class FolderSavingNotificationHandler : INotificationHandler<FolderSavingNotification>
    {
        public void Handle(FolderSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class FormCreatedNotificationHandler : INotificationHandler<FormCreatedNotification>
    {
        public void Handle(FormCreatedNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class FormCreatingNotificationHandler : INotificationHandler<FormCreatingNotification>
    {
        public void Handle(FormCreatingNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class FormDeletedNotificationHandler : INotificationHandler<FormDeletedNotification>
    {
        public void Handle(FormDeletedNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class FormDeletingNotificationHandler : INotificationHandler<FormDeletingNotification>
    {
        public void Handle(FormDeletingNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class FormPrePopulateNotificationHandler : INotificationHandler<FormPrePopulateNotification>
    {
        public void Handle(FormPrePopulateNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class FormSavingNotificationHandler : INotificationHandler<FormSavingNotification>
    {
        public void Handle(FormSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class FormSavedNotificationHandler : INotificationHandler<FormSavedNotification>
    {
        public void Handle(FormSavedNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class FormValidateNotificationHandler : INotificationHandler<FormValidateNotification>
    {
        public void Handle(FormValidateNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class PrevalueSourceCreatedNotificationHandler : INotificationHandler<PrevalueSourceCreatedNotification>
    {
        public void Handle(PrevalueSourceCreatedNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class PrevalueSourceCreatingNotificationHandler : INotificationHandler<PrevalueSourceCreatingNotification>
    {
        public void Handle(PrevalueSourceCreatingNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class PrevalueSourceDeletedNotificationHandler : INotificationHandler<PrevalueSourceDeletedNotification>
    {
        public void Handle(PrevalueSourceDeletedNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class PrevalueSourceDeletingNotificationHandler : INotificationHandler<PrevalueSourceDeletingNotification>
    {
        public void Handle(PrevalueSourceDeletingNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class PrevalueSourceSavedNotificationHandler : INotificationHandler<PrevalueSourceSavedNotification>
    {
        public void Handle(PrevalueSourceSavedNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class PrevalueSourceSavingNotificationHandler : INotificationHandler<PrevalueSourceSavingNotification>
    {
        public void Handle(PrevalueSourceSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class RecordApprovedNotificationHandler : INotificationHandler<RecordApprovedNotification>
    {
        public void Handle(RecordApprovedNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class RecordCreatingNotificationHandler : INotificationHandler<RecordCreatingNotification>
    {
        public void Handle(RecordCreatingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class RecordDeletedNotificationHandler : INotificationHandler<RecordDeletedNotification>
    {
        public void Handle(RecordDeletedNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class RecordDeletingNotificationHandler : INotificationHandler<RecordDeletingNotification>
    {
        public void Handle(RecordDeletingNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class RecordFetchingNotificationHandler : INotificationHandler<RecordFetchingNotification>
    {
        public void Handle(RecordFetchingNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class RecordSavingNotificationHandler : INotificationHandler<RecordSavingNotification>
    {
        public void Handle(RecordSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class RecordStateChangeNotificationHandler : INotificationHandler<RecordStateChangeNotification>
    {
        public void Handle(RecordStateChangeNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class RecordSubmittedNotificationHandler : INotificationHandler<RecordSubmittedNotification>
    {
        public void Handle(RecordSubmittedNotification notification)
        {
            var thing = notification.Form;
        }
    }

    public class WorkflowCreatedNotificationHandler : INotificationHandler<WorkflowCreatedNotification>
    {
        public void Handle(WorkflowCreatedNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class WorkflowCreatingNotificationHandler : INotificationHandler<WorkflowCreatingNotification>
    {
        public void Handle(WorkflowCreatingNotification notification)
        {
            var thing = notification.CreatedEntity;
        }
    }

    public class WorkflowDeletedNotificationHandler : INotificationHandler<WorkflowDeletedNotification>
    {
        public void Handle(WorkflowDeletedNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class WorkflowDeletingNotificationHandler : INotificationHandler<WorkflowDeletingNotification>
    {
        public void Handle(WorkflowDeletingNotification notification)
        {
            var thing = notification.DeletedEntities;
        }
    }

    public class WorkflowExecutionCancelledNotificationHandler : INotificationHandler<WorkflowExecutionCancelledNotification>
    {
        public void Handle(WorkflowExecutionCancelledNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class WorkflowExecutionCompletedNotificationHandler : INotificationHandler<WorkflowExecutionCompletedNotification>
    {
        public void Handle(WorkflowExecutionCompletedNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class WorkflowExecutionFailedNotificationHandler : INotificationHandler<WorkflowExecutionFailedNotification>
    {
        public void Handle(WorkflowExecutionFailedNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class WorkflowExecutionNotConfiguredNotificationHandler : INotificationHandler<WorkflowExecutionNotConfiguredNotification>
    {
        public void Handle(WorkflowExecutionNotConfiguredNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class WorkflowExecutionStartedNotificationHandler : INotificationHandler<WorkflowExecutionStartedNotification>
    {
        public void Handle(WorkflowExecutionStartedNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class WorkflowSavedNotificationHandler : INotificationHandler<WorkflowSavedNotification>
    {
        public void Handle(WorkflowSavedNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class WorkflowSavingNotificationHandler : INotificationHandler<WorkflowSavingNotification>
    {
        public void Handle(WorkflowSavingNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }

    public class DataSourceCreatedNotificationHandler : INotificationHandler<DataSourceCreatedNotification>
    {
        public void Handle(DataSourceCreatedNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class DataSourceCreatingNotificationHandler : INotificationHandler<DataSourceCreatingNotification>
    {
        public void Handle(DataSourceCreatingNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class DataSourceDeletedNotificationHandler : INotificationHandler<DataSourceDeletedNotification>
    {
        public void Handle(DataSourceDeletedNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class DataSourceDeletingNotificationHandler : INotificationHandler<DataSourceDeletingNotification>
    {
        public void Handle(DataSourceDeletingNotification notification)
        {
            var thing = notification.State;
        }
    }

    public class DataSourceSavedNotificationHandler : INotificationHandler<DataSourceSavedNotification>
    {
        public void Handle(DataSourceSavedNotification notification)
        {
            var thing = notification.SavedEntities;
        }
    }
}

and...

using My.Notifications;
using Umbraco.Cms.Core.DependencyInjection;
using Umbraco.Forms.Core.Services.Notifications;

namespace My.Extensions
{
    public static class UmbracoBuilderExtensions
    {
        public static IUmbracoBuilder AddNotificationHandlers(this IUmbracoBuilder builder)
        {
            builder.AddNotificationHandler<DataSourceSavingNotification, DataSourceSavingNotificationHandler>();
            builder.AddNotificationHandler<FolderCreatedNotification, FolderCreatedNotificationHandler>();
            builder.AddNotificationHandler<FolderCreatingNotification, FolderCreatingNotificationHandler>();
            builder.AddNotificationHandler<FolderDeletedNotification, FolderDeletedNotificationHandler>();
            builder.AddNotificationHandler<FolderDeletingNotification, FolderDeletingNotificationHandler>();
            builder.AddNotificationHandler<FolderSavedNotification, FolderSavedNotificationHandler>();
            builder.AddNotificationHandler<FolderSavingNotification, FolderSavingNotificationHandler>();
            builder.AddNotificationHandler<FormCreatedNotification, FormCreatedNotificationHandler>();
            builder.AddNotificationHandler<FormCreatingNotification, FormCreatingNotificationHandler>();
            builder.AddNotificationHandler<FormDeletedNotification, FormDeletedNotificationHandler>();
            builder.AddNotificationHandler<FormDeletingNotification, FormDeletingNotificationHandler>();
            builder.AddNotificationHandler<FormPrePopulateNotification, FormPrePopulateNotificationHandler>();
            builder.AddNotificationHandler<FormSavedNotification, FormSavedNotificationHandler>();
            builder.AddNotificationHandler<FormSavingNotification, FormSavingNotificationHandler>();
            builder.AddNotificationHandler<FormValidateNotification, FormValidateNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceCreatedNotification, PrevalueSourceCreatedNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceCreatingNotification, PrevalueSourceCreatingNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceDeletedNotification, PrevalueSourceDeletedNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceDeletingNotification, PrevalueSourceDeletingNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceSavedNotification, PrevalueSourceSavedNotificationHandler>();
            builder.AddNotificationHandler<PrevalueSourceSavingNotification, PrevalueSourceSavingNotificationHandler>();
            builder.AddNotificationHandler<RecordApprovedNotification, RecordApprovedNotificationHandler>();
            builder.AddNotificationHandler<RecordCreatingNotification, RecordCreatingNotificationHandler>();
            builder.AddNotificationHandler<RecordDeletedNotification, RecordDeletedNotificationHandler>();
            builder.AddNotificationHandler<RecordDeletingNotification, RecordDeletingNotificationHandler>();
            builder.AddNotificationHandler<RecordFetchingNotification, RecordFetchingNotificationHandler>();
            builder.AddNotificationHandler<RecordSavingNotification, RecordSavingNotificationHandler>();
            builder.AddNotificationHandler<RecordStateChangeNotification, RecordStateChangeNotificationHandler>();
            builder.AddNotificationHandler<RecordSubmittedNotification, RecordSubmittedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowCreatedNotification, WorkflowCreatedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowCreatingNotification, WorkflowCreatingNotificationHandler>();
            builder.AddNotificationHandler<WorkflowDeletedNotification, WorkflowDeletedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowDeletingNotification, WorkflowDeletingNotificationHandler>();
            builder.AddNotificationHandler<WorkflowExecutionCancelledNotification, WorkflowExecutionCancelledNotificationHandler>();
            builder.AddNotificationHandler<WorkflowExecutionCompletedNotification, WorkflowExecutionCompletedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowExecutionFailedNotification, WorkflowExecutionFailedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowExecutionNotConfiguredNotification, WorkflowExecutionNotConfiguredNotificationHandler>();
            builder.AddNotificationHandler<WorkflowExecutionStartedNotification, WorkflowExecutionStartedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowSavedNotification, WorkflowSavedNotificationHandler>();
            builder.AddNotificationHandler<WorkflowSavingNotification, WorkflowSavingNotificationHandler>();
            builder.AddNotificationHandler<DataSourceCreatedNotification, DataSourceCreatedNotificationHandler>();
            builder.AddNotificationHandler<DataSourceCreatingNotification, DataSourceCreatingNotificationHandler>();
            builder.AddNotificationHandler<DataSourceDeletedNotification, DataSourceDeletedNotificationHandler>();
            builder.AddNotificationHandler<DataSourceDeletingNotification, DataSourceDeletingNotificationHandler>();
            builder.AddNotificationHandler<DataSourceSavedNotification, DataSourceSavedNotificationHandler>();

            return builder;
        }
    }
}