A Quick Way to Send Email Invitation Using ASP.NET MVC

First we're going to update our Model so that it can hold the data needed for, what I believe, are the minimum requirements for an invitation.
Add the following code to the EmailModel.cs file:

1. public string Location { get; set; }
2. public DateTime StartTime { get; set; }
3. public DateTime EndTime { get; set; }
4. public DateTime Date { get; set; }
5. public string Summary { get; set; }
6. public string Description { get; set; }

The above code is pretty self-explanatory, maybe the public string Summary and the public string Description aren't. The one is kind of the name of the event/meeting/invitation/whatever and the other is or can be a lengthy description of the invitation respectively.

Your Model should bare a resemblance to this when you're done:

1. public string Name { get; set; }
2. public string Addess { get; set; }
3. public string Subject { get; set; }
4. public string Body { get; set; }
5. public string Location { get; set; }
6. public DateTime StartTime { get; set; }
7. public DateTime EndTime { get; set; }
8. public DateTime Date { get; set; }
9. public string Summary { get; set; }
10. public string Description { get; set; }

Open the Index.cshtml View and add these lines of code after the form fields and before the submit button we had previously created:

1. <label asp-for="Location">Location</label> <br />
2. <input asp-for="Location" type="text" name="Location" /> <br />
3. <label asp-for="Date">Date</label> <br />
4. <input asp-for="Date" type="date" name="Date" /><br />
5. <label asp-for="StartTime">Start Time</label> <br />
6. <input asp-for="StartTime" type="time" name="StartTime" /><br />
7. <label asp-for="EndTime">End Time</label> <br />
8. <input asp-for="EndTime" type="time" name="EndTime" /><br />
9. <label asp-for="Summary">Summary</label> <br />
10. <input asp-for="Summary" type="text" name="Summary" /><br />
11. <label asp-for="Description">Description</label> <br />
12. <textarea asp-for="Description" type="" name="Description"></textarea> <br />

The last I checked, some form controls don't work as intented in IE. I think the date and time input fields work just like plain old text fields if I'm not mistaken.

The more complex part is up next and the code is quite lengthy. I'd say I'll explain but some of the lines are waaaay over my head but I'll try my best to explain.

1. DateTime date = emailModel.Date;
2. DateTime startTime = emailModel.StartTime;
3. DateTime endTime = emailModel.EndTime;
4. string now = DateTime.Now.ToString("yyyyMMddTHHmmssZ");
6. string ics = string.Format(
7.  "BEGIN:VCALENDAR\r\n" +
8.  "PRODID:-//Comapany & Co.//Their Application//EN\r\n" +
9.  "VERSION:2.0\r\n" +
10.  "METHOD:REQUEST\r\n" +
11.  "BEGIN:VEVENT\r\n" +
12.  "CREATED:{0}\r\n" +
13.  "DTSTART:{1}\r\n" +
14.  "DTEND:{2}\r\n" +
15.  "DTSTAMP:{3}\r\n" +
16.  "UID:{4}\r\n" +
17.  "ATTENDEE;CN=\"{5}\";RSVP=TRUE:mailto:{6}\r\n" +
18.  "X-ALT-DESC;FMTTYPE=text/html:{7}\r\n" +
19.  "LOCATION:{8}\r\n" +
20.  "ORGANIZER;CN=\"Mailer App Name Here\":mailto:[[The email address that the ivitation is being sent from]]\r\n" +
21.  "SEQUENCE:0\r\n" +
22.  "SUMMARY:{9}\r\n" +
23.  "TRANSP:OPAQUE\r\n" +
24.  "END:VEVENT\r\n" +
25.  "END:VCALENDAR",
26.  now,
27.  string.Concat(date.Year, date.Month.ToString("D2"), date.Day.ToString("D2"), "T", startTime.Hour.ToString("D2"), startTime.Minute.ToString("D2"), startTime.Second.ToString("D2")),
28.  string.Concat(date.Year, date.Month.ToString("D2"), date.Day.ToString("D2"), "T", endTime.Hour.ToString("D2"), endTime.Minute.ToString("D2"), endTime.Second.ToString("D2")),
29.  now,
30.  Guid.NewGuid(),
31.  emailModel.Name,
32.  emailModel.Addess,
33.  emailModel.Description,
34.  emailModel.Location,
35.  emailModel.Summary);
37. ContentType contentType = new ContentType("text/calendar");
38. contentType.Parameters.Add("method", "REQUEST");
39. contentType.Parameters.Add("name", "invitation.ics");
40. byte[] bytes = Encoding.UTF8.GetBytes(ics);
41. MemoryStream stream = new MemoryStream(bytes);
42. Attachment icsAttachment = new Attachment(stream, "invitation.ics", "text/calendar");
44. mailMessage.Attachments.Add(icsAttachment);

Okay okay, 40+ lines of code is a bit excessive to stomach in one sitting but lines 7 - 25 is what we really came here for. These lines are where we're building our ical file. Directly below I'll list and have a link to what most of these properties are if you're extra curious.

Property List

I'm gonna skip some lines when it comes to the explanation of the Properties (lines 7 - 25) but you're free to follow the links I provided above if you're feeling a little uncertain.

• In lines 1 - 3 we're just assigning our dates and times to variables to lessen the mess that will come later.
• Line 4 we're setting the date/time format because the ical format is extremely specific. Dates need to adhere to this format: yyyyMMddTHHmmssZ.
• In line 6 we're creating our string, if you prefer StringBuilder and appending new lines then it will still work.
• Line 7 is where we start or open our ical.
• Line 17 is where we say who's attending. If you're sending an invitation to multiple recipients you'll have to write this line out for each recipient. You can accomplish this with some kind of looping function to iterate through each one. Also take note of the RSVP=TRUE if you're interested in requesting a response.
• In place of line 18, I've seen examples of DESCRIPTION instead of X-ALT-DESC. Apparently it allows for HTML.
• Line 20 you need to note that if the emails for Attendee and Organizer are the same, the Organizer won't be able to accept (obvious I know but it took me longer than I want to admit to figure that out).

It won't be enought to just add \n at the end of each line (lines 7 - 24) because it won't adhere to the format specifications so be sure to use \n\r.

• Lines 27 and 28 is a bit messing because we want to get the date of the meeting as well as the start and end times and also format it in the yyyyMMddTHHmmssZ format.
• Lines 37 - 39 are SUPER important and I've struggled to understand why the .ics file was only attached but the email itself wasn't recognized as an invitation. This article saved my life. You need to specify that what you're sending is of type text/calendar.
• Lines 40 - 44 is where we build and attached our ical in .ics format.

Full Code