I am trying to get a custom workflow working where I want to create a node based on a form selection.

I have this code

public override WorkflowExecutionStatus Execute(Record record, RecordEventArgs e)
        {
            record.State = FormState.Approved;

            var contentService = Current.Services.ContentService;
            var parentNode = Guid.Parse("ff3e93f6-b34f-4664-a08b-d2eae2a0adbd");

            var dateField = e.Record.GetRecordFieldByAlias("selectedDate");
            var timeField = e.Record.GetRecordFieldByAlias("selectedTime");

            var nodeExists = Umbraco.Content(parentNode).DescendantsOfType("appointmentItemDate").Where(x => x.Name == theDate);
            var dateItem = contentService.Create(dateField.ValuesAsString(), parentNode, "appointmentItemDate");
            contentService.SaveAndPublish(dateItem);

            return WorkflowExecutionStatus.Completed;

            //Current.Logger.Debug<TimeDateWorkflowType>("The record with unique id {RecordId} that was submitted via the Form {FormName} with id {FormId} has been changed to {RecordState} state",
            //   record.UniqueId, e.Form.Name, e.Form.Id, "approved");

        }

The problem is this one

var nodeExists = Umbraco.Content(parentNode).DescendantsOfType("appointmentItemDate").Where(x => x.Name == theDate);

The type or namespace name 'Content' does not exist in the namespace 'Umbraco' (are you missing an assembly reference?)

How can I access published nodes in this workflow?

I want to check if there already exists a node with a given name, f.x. "29-05-2021" and then not create a new node with that name.