Multi- User/ Resource Web Diary System With Repeat Events

The Index.cshtml page contains a model ‘FullCal.ViewModels.Resource’. This can carry any information you want. This example uses it to carry the ‘Default View’ to be shown to the user when the page reloads, and the title string for the resource column. In the controller, once we decide/set the view to use, we send back the ‘ResourceView’ as a string in the view model. The last thing to note about ‘ResourceView’ is that it is stored as a ‘Session value’. See controller method ‘setView’ (below) for the implementation.

1. Index controller
   1. public class HomeController: Controller
   2. {
   3. TestHarness testHarness;
   4. // used to store temp data repository public ActionResult
   5. Index(string ResourceView)
   6. {
   7. // create test harness if it does not exist
   8. // this harness represents interaction you may replace with database calls.
   9. if (Session["ResourceView"]!=null)
   10. // refers to whatever default view you may have,
   11. // for example Offices/Users/Shared Equipment/etc
   12. // you can create any amount and combination
   13. // of different view types you need.
   14. ResourceView = Session["ResourceView"].ToString();
   15. if (!System.IO.File.Exists(utils.GetTestFileLocation()))
   16. {
   17. testHarness = new TestHarness();
   18. testHarness.Setup();
   19. utils.Save(utils.GetTestFileLocation(), testHarness);
   20. }
   21. if (ResourceView == null) ResourceView = "";
   22. ResourceView = ResourceView.ToLower().Trim();
   23. var DiaryResourceView = new Resource();
   24. if (ResourceView == "" || ResourceView == "employees")
   25. // set the default
   26. {
   27. DiaryResourceView.DefaultView = "employees";
   28. DiaryResourceView.ResourceTitle = "Branch offices";
   29. }
   30. else if
   31. (
   32. ResourceView == "equipment")
   33. {
   34. DiaryResourceView.DefaultView = ResourceView;
   35. DiaryResourceView.ResourceTitle = "Equipment list";
   36. }
   37. return View(DiaryResourceView);
   38. }
2. SetView controller
   1. // this method, called from the index page, sets a session variable for
   2. // the user that gets looped back to the index page to tell it what view
   3. // to display. branch/employee or Equipment.
   4. public ActionResult setView(string ResourceView)
   5. {
   6. Session["ResourceView"] = ResourceView; return RedirectToAction("Index");
   7. }

In this example, we don't allow users to click on "office" rows, so we raise an alert if the user makes a mistake...

Drag and drop

Having the capability to be able to drag/drop events onto a diary is useful. However, we need to be able to tell the diary on the drop event, something about the event being dropped. For this, we attach information to the object being dropped in a particular manner.

Repeat / recurring calendar events

The final thing I want to demonstrate is how we can put repeat or recurring events into our solution. I have done this using a combination of two very useful open course libraries. One that operates browser-side, one server-side. Before we look at the code and components we use, it would be good to understand how repeats work and how we can represent recurring events in our solution.

Understanding CRON format

A CRON JOB (from chronological), is well known in the UNIX operating system as a command to tell the system to execute a job at a particular time. CRON has a syntax that when formulated, both a computer and human can read, it describes the exact date/time a job should be triggered and is very flexible. A CRON string is not restricted to describing a single date and time (example: 1st Jan 2016), it can also be used to describe recurring time patterns (example: The third of each month at 9am). There are a few different implementations of the CRON syntax, and you can expand to it yourself if you need to. For example, if a basic CRON descriptor only allowed for repeat events, you might decide to add limitations of a 'between X and Y date' to your business logic (ie: 'The third of each month at 9am, but only if thats a Tuesday and between the 1st of June 2016 and the 30th of August 2016).Standard CRON consists of five fields, each separated by a space, minute hour day-of-month month-of-year day-of-week. Each field can contain one or more characters that describe the contents of the field,

• * (asterisk) means all values. For example, if we had '*' in the minute field, it would mean 'execute the job once per minute'. If it was in the month field, it would mean 'execute the job once per month'.
• commas in a field are used to separate values (eg: 2,4,6 .. on the 2nd, 4th and 6th minute)
• hyphens in a field are used to specify a range (eg: 4-9 .. between the 4th and 9th minute)
• after an asterisk or hyphen-range, we can use the forward slash '/' to indicate that values are repeated over and over with a particular interval between the values. (eg: 0-18/2 indicates execute the job every two hours between the time 0 hours and 18 hours)

NCronTab

Ok, so we have have the building and storage of the repeat/recurring event information and the UI taken care of - now lets look at what we can do to decide WHEN/IF to display these recurring events in our diary. In UNIX, a CronTab is a file that contains a list of CRON expressions, and a command for the system to execute once that CRON time gets triggered. From a Windows perspective, the equivalent is the Windows task scheduler service. NCrontab is a library written in C# 6.0 that provides the following facilities,

• Parsing of crontab expressions
• Formatting of crontab expressions
• Calculation of occurrences of time based on a crontab schedule

1. the user decides to refresh the diary to show events in a particular date range. Note the params sent in are the start and end date plus the resourceView required.
   1. public JsonResult GetScheduleEvents(string start, string end, string resourceView) .. <etc>
2. we query all scheduled events for any event that has a 'repeat' value stored.
   1. repeatEvents = testHarness.ScheduleEvents.Where(s => (s.repeat != null));
3. we then examine each repeat event (ie: the CRON string expression), and PARSE it with NCronTab.CrontabSchedule, passing the result of the parse into a method that says 'between this start and end date given, give me a list of valid date/times the CRON string represents.
   1. if (repeatEvents != null) foreach(var rptEvnt in repeatEvents)
   2. {
   3. var schedule = CrontabSchedule.Parse(rptEvnt.repeat);
   4. var nextSchdule = schedule.GetNextOccurrences(Start, End);
   5. foreach(var startDate in nextSchdule) {
   6. ScheduleEvent itm = new ScheduleEvent();
   7. itm.id = rptEvnt.EventID;
   8. if (rptEvnt.title.Trim() == "") itm.title = rptEvnt.clientName;
   9. else itm.title = rptEvnt.title;
   10. itm.start = startDate.ToString("s");
   11. itm.end = startDate.AddMinutes(30).ToString("s");
   12. itm.duration = rptEvnt.duration.ToString();
   13. itm.notes = rptEvnt.notes;
   14. itm.statusId = rptEvnt.statusId;
   15. itm.statusString = rptEvnt.statusString;
   16. itm.allDay = false;
   17. itm.EmployeeId = rptEvnt.EmployeeId;
   18. itm.clientId = rptEvnt.clientId;
   19. itm.clientName = rptEvnt.clientName;
   20. itm.equipmentId = rptEvnt.equipmentID;
   21. itm.EmployeeName = rptEvnt.EmployeeName;
   22. itm.repeat = rptEvnt.repeat;
   23. itm.color = rptEvnt.statusString;
   24. if (resourceView == "employees") itm.resourceId = rptEvnt.EmployeeId;
   25. else itm.resourceId = rptEvnt.equipmentID;
   26. EventItems.Add(itm);
   27. }
   28. }