Click here to Skip to main content
Click here to Skip to main content

A Basic Scheduler

, 28 May 2008 CPOL
Rate this:
Please Sign up or sign in to vote.
Define schedules to the program for executing programmer defined jobs


I needed a simple scheduler to execute on an exact time / time span for generating automated reports. I checked various articles and the Internet for a scheduler that could tick off exactly as required and if it failed, then at the nearest next time.


While searching the Internet, I found an article by Andy Brummer which provided me with quite a few ideas to go about the code, but I needed something much more simpler, so it did not solve my purpose. Moreover, I was programming in VB.NET and the supplied codes were in C#, which on the whole would make it difficult for me to implement.

Before we continue any further, it would be a great help if you could read about delegates, calling and storing. I would suggest that you read a good article by Abhishek Khanna on delegates. It is a very important addition in VB.NET and simplifies many issues.

I would also suggest that you go through the Microsoft Library - MSDN about delegates, it's a very resourceful guide for quite a few programming issues.


The entire code block is wrapped within a class named Scheduler. It is dependant on three objects, namely:

  1. System.Windows.Forms.Timer
  2. System.Collections.ArrayList
  3. System.Data.DataTable

The DataTable is used for storing all events happening in the duration. This is done so as to allow immediate changes in the values. I had tried using ArrayList and other collection objects, but I did not get proper results doing so.

SetSchedule.Columns.Add(New DataColumn("SchType", System.Type.GetType("System.String")))
SetSchedule.Columns.Add(New DataColumn
    ("exeTime", System.Type.GetType("System.DateTime")))
SetSchedule.Columns.Add(New DataColumn("active", System.Type.GetType("System.Boolean")))
SetSchedule.Columns.Add(New DataColumn
    ("NextexeTime", System.Type.GetType("System.DateTime")))
SetSchedule.Columns.Add(New DataColumn
    ("TimeDiff", System.Type.GetType("System.TimeSpan")))

I added these five fields to the DataTable for keeping a track of the schedule, and I enumerated the following:

    Public Enum Scheduled
        Once = 1
        BySecond = 2
        ByMinute = 4
        ByHour = 8
        Daily = 16
        Weekly = 32
        Monthly = 64
        Yearly = 128
        Regular = 256
    End Enum

I used an ArrayList to store all events to execute on the scheduler match.

Using the Code

Add the class project to your solution and take a reference to it in your project.

Declare a variable as follows:

Dim sch As New Scheduler.Scheduler

Declare and allocate your delegates to functions and Subs:

    'Declare a Delegate without Parameters
    Delegate Sub ShowMessage()
    'Declare a Delegate With Parameters
    Delegate Sub ShowMessageBox(ByVal str As String)

    'Define a Sub/Function without Parameters
    Private Sub DisplayMessage()
        RichTextBox1.Text += "It is time: " + Now.ToString + vbCrLf
    End Sub

    'Define a Sub/Function with Parameters
    Private Sub DisplayMessageBox(ByVal str As String)
        MsgBox("It is time: " + Now.ToString)
    End Sub

    'Pass a Delegate without Parameters
    Dim msd As ShowMessage = AddressOf DisplayMessage

    'Pass a Delegate with Parameters
    Dim msd1 As ShowMessageBox = AddressOf DisplayMessageBox 

Set the scheduler timers:

'Add a Schedule to Do the Events On a Particular Date/Time
'Add a Schedule to do the Events, after every Time Span
sch.AddSchedule(New TimeSpan(0, 5, 0))
'Add a Schedule to do the Events, after every Time Span starting from Date/Time
sch.AddSchedule(#5/28/2008 4:00:00 AM#, New TimeSpan(0, 5, 0))
'Add a Schedule to do the Events, EveryDay at the Said Times in 24Hrs Clock
sch.AddSchedule("09:25", "21:25")

Declare the events:

sch.AddEvent(msd1, "Test String")

Start the scheduler:



  • 28th May, 2008: First release

Contact Me

In case you have any problems with the code, you can contact me at or on my IM (Instant Messenger)


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Didara F Dosabhai
Database Developer Wizard Enterprise Pvt Ltd
India India
Database Developer

Comments and Discussions

QuestionMessage Automatically Removed PinmemberSai Pranad12-May-14 10:06 
QuestionA couple more examples? Pinmemberbeckerben10-Oct-08 18:57 
Generalin practice use whats built in to windows or linux PinmemberLeblanc Meneses2-Jun-08 9:35 
GeneralRe: in practice use whats built in to windows or linux PinmemberNoctris24-Jul-08 7:20 
GeneralRe: in practice use whats built in to windows or linux PinmemberLeblanc Meneses24-Jul-08 9:30 
GeneralRe: in practice use whats built in to windows or linux PinmemberNoctris8-Oct-08 1:27 
GeneralRe: in practice use whats built in to windows or linux PinmemberLeblanc Meneses8-Oct-08 11:10 
GeneralDatabase enabled.... PinmemberStewart Roberts30-May-08 8:14 
GeneralNice work Pinmemberdnpro30-May-08 4:34 
GeneralLets state the obvious [modified] Pinmember Programm3r 28-May-08 20:50 
GeneralTypo in title Pinmember leppie 28-May-08 7:49 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web04 | 2.8.141223.1 | Last Updated 28 May 2008
Article Copyright 2008 by Didara F Dosabhai
Everything else Copyright © CodeProject, 1999-2014
Layout: fixed | fluid