C# console app to send email at scheduled times

Question

I\'ve got a C# console app running on Windows Server 2003 whose purpose is to read a table called Notifications and a field called \"NotifyDateTime\" and send an email when

Answer 1

Scheduled tasks can be scheduled to run just once at a specific time (as opposed to hourly, daily, etc.), so one option would be to create the scheduled task when the specific field in your database changes.

You don't mention which database you use, but some databases support the notion of a trigger, e.g. in SQL: http://technet.microsoft.com/en-us/library/ms189799.aspx

Answer 2

I have been dealing with the same problem about three years ago. I have changed the process several times before it was good enough, I tell you why:

1. First implementation was using special deamon from webhosting which called the IIS website. The website checked the caller IP and then check the database and send emails. This was working until one day, when I got a lot of very dirty emails from the users that I have totally spammed their mailboxes. The drawback of keeping email in database and sending from SMTP email is that there is NOTHING which ensure DB to SMTP transaction. You are never sure if the email has been successfully sent or not. Sending email can be successfull, can failed or it can be false positive or it can be false negative (SMTP client tells you, that the email was not sent, but it was). There was some problem with SMTP server and the server returned false(email not send), but the email was sent. The daemon was resending the email every hour the whole day before the dirty emails appears.

2. Second implementation: To prevent spamming, I have changed the algorithm, that the email is considered to be sent even if it failed (my email notification was not too important). My first advice is: "Don't launch the deamon too often, because this false negative smtp error makes users upset."

3. After several month there were some changes on the server and the daemon was not working well. I got the idea from the stackoverflow: bind the .NET timer to the web application domain. It wasn't good idea, because it seems, that IIS can restart application from time to time because of memory leaks and the timer never fires if the restarts are more often then timer ticks.

4. The last implementation. Windows scheduler every hour fires python batch which read local website. This fire ASP.NET code. The advantage is that time windows scheduler call the the local batch and website reliably. IIS doesn't hang, it has restart ability. The timer site is part of my website, it is still one projects. (you can use console app instead). Simple is better. It just works!