Using Refresh Token

here is where I am getting my model, the dbxService is where I send the refreshToken value as show in the previus message

public async Task<FileManagerViewModel> GetDropboxViewModel(Panther.Views.Attachment.IndexViewModel gridViewModel, IIdentityService identityService)
        {
            var dbxViewModel = new FileManagerViewModel();
            dbxViewModel.Type = FileManagerProviderType.Dropbox;
            Project project = null;
            var dropBoxsettings = await _unitOfWork.DropBoxSettingsRepository.GetSettingsByTenantId(identityService.Tenant.Id).FirstAsync().ConfigureAwait(false);
            var path = "/MyCompany";
            MyCompanyLogger.Log(MyCompanyLogLevel.Info, "BlobRepository: GetDropboxViewModel", $"GridViewModel: {Newtonsoft.Json.JsonConvert.SerializeObject(gridViewModel)}");

            try
            {
                var dbxService = new Panther.Services.DropboxService(dropBoxsettings);
                FolderMetadata folder = null;
                if (gridViewModel.AccountGuid.HasValue)
                {
                    var account = await _unitOfWork.AccountRepository.GetAccount(identityService, gridViewModel.AccountGuid.Value, AccessLevelAction.Details).FirstAsync().ConfigureAwait(false);
                    folder = await dbxService.GetFolder(account.DropboxFolderId, account.NameAndNumber);
                    if (account.DropboxFolderId != folder.Id)
                    {
                        account.DropboxFolderId = folder.Id;
                        await _unitOfWork.AccountRepository.InsertOrUpdateAndSaveAsync(account).ConfigureAwait(false);
                        MyCompanyLogger.Log(MyCompanyLogLevel.Info, "BlobRepository: GetDropboxViewModel", $"Account updated Dropbox folder Id: {account.DropboxFolderId}");
                    }
                    path = folder.PathLower;
                }
                if (gridViewModel.ProjectGuid.HasValue)
                {
                    project = await _unitOfWork.ProjectRepository.GetProject(identityService, gridViewModel.ProjectGuid.Value, AccessLevelAction.Details).FirstAsync().ConfigureAwait(false);
                    folder = await dbxService.GetFolder(project.DropboxFolderId, project.NameAndNumber, project.Account.DropboxFolderId, project.Account.NameAndNumber);
                    if (project.DropboxFolderId != folder.Id)
                    {
                        project.DropboxFolderId = folder.Id;
                        await _unitOfWork.ProjectRepository.InsertOrUpdateAndSaveAsync(project).ConfigureAwait(false);
                        MyCompanyLogger.Log(MyCompanyLogLevel.Info, "BlobRepository: GetDropboxViewModel", $"Project updated Dropbox folder Id: {project.DropboxFolderId}");
                    }
                    path = folder.PathLower;
                }

                var provider = new DropboxFileSystemProvider(path);
                DevExpress.Web.AccountManager.RegisterDropbox("Dropbox1", "AccessTokenValue1");
                provider.AccessTokenValue = Backoffice.Encryptor.Decrypt(dropBoxsettings.AuthToken);
                provider.AccountName = Backoffice.Encryptor.Decrypt(dropBoxsettings.AuthToken);
                dbxViewModel.FileSystemProvider = provider;

                dbxViewModel.IsAllowCreate = HasAccess(FilePermissions.Create, identityService, project);
                dbxViewModel.IsAllowDelete = HasAccess(FilePermissions.Delete, identityService); 
                dbxViewModel.IsAllowEdit = HasAccess(FilePermissions.Delete, identityService);
                dbxViewModel.IsAllowDownload = HasAccess(FilePermissions.Download, identityService);
            }
            catch (Exception ex)
            {
                Backoffice.ErrorHelper.LogErrorManually(ex);
                MyCompanyLogger.Log(MyCompanyLogLevel.Error, "BlobRepository: GetDropboxViewModel exception", ex);
            }
            return dbxViewModel;
        }

 but here

provider.AccessTokenValue = Backoffice.Encryptor.Decrypt(dropBoxsettings.AuthToken);

I ma getting a message that says that AccessTokenValue is obsolete, I am unable to find any example of how to use:

can you tell me where is wrong the code please?