Scheduled Notifications in Windows 10 VB.Net - vb.net

Question

I am working on a project where the user sets a reminder with information, date and time for when a notification should pop up and the notification should be clickable and open another form with the reminder information on it. So far I can set the reminder but it pops up as soon as the remind button in clicked, my notification looks a standard windows 10 notification, I just want the notification to be scheduled for a certain date and time. The information including date and time is saved into an Access Database. I am using VB.Net
Kind Regards
Form:
This is my reminder form as of now
This is how my notification looks like
Imports System.Data.OleDb
Public Class frmReminder
Private CurrentReminderID As Integer = -1
Private Sub frmReminder_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BtnClear.PerformClick()
Timer1.Enabled = True
End Sub
Private Sub BtnClear_Click(sender As Object, e As EventArgs) Handles BtnClear.Click
Label6.Text = ""
TxtCustName.Text = ""
TxtDeviceInfo.Text = ""
TxtPrice.Text = ""
TxtDateDue.ResetText()
End Sub
Private Sub BtnSetReminder_Click(sender As Object, e As EventArgs) Handles BtnSetReminder.Click
If DbConnect() Then
Dim SQLCmd As New OleDbCommand
If CurrentReminderID = -1 Then
With SQLCmd
.Connection = cn
.CommandText = "Insert into TblReminder (CustomerName, DeviceInfo, RepairPrice, ReminderDate)"
.CommandText &= "Values (#CustomerName, #DeviceInfo, #RepairPrice, #ReminderDate)"
.Parameters.AddWithValue("#CustomerName", TxtCustName.Text)
.Parameters.AddWithValue("#DeviceInfo", TxtDeviceInfo.Text)
.Parameters.AddWithValue("#RepairPrice", TxtPrice.Text)
.Parameters.AddWithValue(" #ReminderDate", TxtDateDue.Text)
.ExecuteNonQuery()
.CommandText = "Select ##Identity"
CurrentReminderID = .ExecuteScalar
Label6.Text = CurrentReminderID
End With
End If
End If
Notification.ShowBalloonTip(1000, "Reminder", "Customer Order Due!", ToolTipIcon.None)
End Sub
End Class

Answer 1

You need to use a Timer and to avoid the constant reading of the database you may use something very simple as a DateTimePicker or a TextBox. In this example I'll use a Texbox.
So, insert a TextBox1 in your form and had the value of the first date/time (read from your database just once). The Textbox1 text should be something like "2021-10-21 15:00" (don't put the seconds and don't forget to have a space between date and time)
TextBox1.Text="2021-10-21 15:00" ' read this data from your database
Then you need to insert a Timer in your form and add this values:
Timer1.Interval = 60000 ' 1 minute
Timer1.Enabled = True
For the last you need to double click the Timer1 and write this code:
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
If TextBox1.Text = Now.ToString("yyyy-MM-dd HH:mm") Then
' At this moment you should read the next date/time and put that in TextBox1
MsgBox("Show the popup notification")
End If
End Sub

Answer 2

Since you are using DB connections, ill assume you are familiar with multi threading.
RULE 1. The easiest way to do this is for your application to keep track of (in RAM) the next notification. Any time you add a new one through your app it will both insert it into the DB as well as check to see if it is going to elapse before the current one in RAM. When the one in RAM expires it grabs the next one from the DB. All that to say, you find a way to ensure that the next one to elapse is kept in RAM at any given time.
RULE 2. Then, when a notification is 'saved' in RAM, compare the time when the notification should be displayed - current time, this will give you how long until the notification should de shown and set a timer for that amount of time.
RULE 3. When the timer has elapsed display the notification for the one that is in RAM (Per rule 1 this is the one that just elapsed). And iterate the DB to find the next one to expire. Rinse and repeat. (Note, youll need to handle edge cases for when the first one is intered as there will not be any to compare to, and for when the last one is notified as there will not be any notifications left to store in RAM)
Tada, sorry i dont have code samples. But that is how i have solved this very issue numerous times. It works quite nicely.
EDIT 1: CODE
'main for testing
Dim notificationScheduler As NotificationScheduler = NotificationScheduler.getInstance
notificationScheduler.insertNotification(New MyNotificationEntity("Yay, working", DateTime.Now.AddSeconds(15)))
' expected that the one below will be displayed since insertNotification will only keep track of the newest one in the queue
' As mentioned in your post, you have a DB to persist them long term and as such will only need one in the APP's RAM at a time
notificationScheduler.insertNotification(New MyNotificationEntity("Yay, working-2", DateTime.Now.AddSeconds(3)))
' myNotificationEntity, will be replaced by whatever class you are using to package your reminder's in a single class (dont see on in your code sample)
Public Class MyNotificationEntity
Public data As String
Public timeToShow As DateTime
' this is a dumb bucket class, you will not end up using this one but rather whatever class you use to contain your notifications
' you will need to add _timeToShow as a variable to your class or change the code in the NotificationScheduler to be compatible with your Notification class
Public Sub New(data As String, timeToShow As DateTime)
Me.data = data
Me.timeToShow = timeToShow
End Sub
End Class
'NotificationScheduler class
Public Class NotificationScheduler
Private Shared _instance As NotificationScheduler
Private Shared ReadOnly _lock As Object = New Object()
Dim queuedNotification As MyNotificationEntity
Dim WithEvents timer As System.Windows.Forms.Timer = New Timer
Dim timerElapsedTime As DateTime = DateTime.Now
Private Sub New()
timer.Enabled = False
End Sub
Public Shared Function getInstance()
' enforce singleton design pattern (i.e. there should only be one of these in existence)
' If this does not make sense, that is fine, at some point lookup the 'singleton design pattern'
' Also, SyncLock is a VB (.net really) element that means in a multi-threaded application only one of them at any given time is inside the SyncLock block,
' the rest are queued to alleviate race conditions. Again, if this does not make sense, lookup 'race conditions'
SyncLock _lock
If (_instance Is Nothing) Then
_instance = New NotificationScheduler()
End If
End SyncLock
Return _instance
End Function
' called after you have placed the new notification in your DB, replaces the currently queued notification only if the new one will be shown first
Public Sub insertNotification(notificationEntity As MyNotificationEntity)
If timerElapsedTime.Ticks < notificationEntity.timeToShow.Ticks Then
queuedNotification = notificationEntity
timer.Stop()
Dim span As TimeSpan = notificationEntity.timeToShow - timerElapsedTime
timer.Interval = CInt(span.TotalMilliseconds)
timer.Start()
End If
End Sub
Private Sub timer_elapsed() Handles timer.Tick
' the notification time has arrived
showNotification()
readNextFromDb()
End Sub
Private Sub readNextFromDb()
' read the next (if any) from the and handle edge cases for when there is not next one in the DB
'IMPORTANT: if the one you read from the DB has already happened (i.e. the notification dateTime is after now, notify and do this method again)
'' your code here
End Sub
Private Sub showNotification()
MsgBox(queuedNotification.data) ' do whatever notification you want
End Sub
End Class
You will need to (it appears) create a class NotificationDAO (Data Access Object) or NotificationDTO (Data Transfer Object) or a generic NotificationEntity. That class will have a constructor and public instance variables for the items you need to store about a notification (i.e. every column you have in the 'TblReminder ' table) and everything should work fairly easily.
Note, the above code does not work nor check for pulling notifications out of a DB that have already passed their notification time, read the comments in the code for further information.