This is an application scheduler that is implemented as a Windows Service, similar to the Windows Task Scheduler - but simple, as it has fewer configuration options and it uses XML to store and retrieve data.
The program uses System.Timers, System.Threading and System.Diagnostics to repeatedly loop through the XML data to see whether an application is scheduled to run at the present time or not, and if yes, to launch it as a new process in a new thread.
The source
Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Data
Imports System.Diagnostics
Imports System.ServiceProcess
Imports System.Xml
Imports System.Timers
Imports System.Threading
Imports System.Configuration
Imports System.IO
Namespace AppScheduler
Public Class AppScheduler
Inherits System.ServiceProcess.ServiceBase
Private configPath As String
Private _timer As New System.Timers.Timer()
Private dsTasks As New DataSet()
Private formatString As String = "MM/dd/yyyy HH:mm:ss"
'/ <summary>
'/ Required designer variable.
'/ </summary>
Private components As System.ComponentModel.Container = Nothing
'/ <summary>
'/ Class that launches applications on demand.
'/ </summary>
Class AppLauncher
Private app2Launch As String
Public Sub New(path As String)
app2Launch = path
End Sub 'New
Public Sub runApp()
Dim pInfo As New ProcessStartInfo(app2Launch)
pInfo.WindowStyle = ProcessWindowStyle.Normal
Dim p As Process = Process.Start(pInfo)
End Sub 'runApp
End Class 'AppLauncher
Sub timeElapsed(sender As Object, args As ElapsedEventArgs)
Dim currTime As DateTime = DateTime.Now
Dim dRow As DataRow
For Each dRow In dsTasks.Tables("task").Rows
Dim runTime As DateTime = Convert.ToDateTime(dRow("time"))
If currTime >= runTime Then
Dim exePath As String = dRow("exePath").ToString()
Dim launcher As New AppLauncher(exePath)
New Thread(New ThreadStart(AddressOf launcher.runApp)).Start()
' Update the next run time
Dim strInterval As String = dRow("repeat").ToString().ToUpper()
Select Case strInterval
Case "D"
runTime = runTime.AddDays(1)
Case "W"
runTime = runTime.AddDays(7)
Case "M"
runTime = runTime.AddMonths(1)
End Select
dRow("time") = runTime.ToString(formatString)
dsTasks.AcceptChanges()
Dim sWrite As New StreamWriter(configPath)
Dim xWrite As New XmlTextWriter(sWrite)
dsTasks.WriteXml(xWrite, XmlWriteMode.WriteSchema)
xWrite.Close()
End If
Next dRow
End Sub 'timeElapsed
Public Sub New()
' This call is required by the Windows.Forms Component Designer.
InitializeComponent()
End Sub 'New
' TODO: Add any initialization after the InitComponent call
' The main entry point for the process
Shared Sub Main()
Dim ServicesToRun() As System.ServiceProcess.ServiceBase
' More than one user Service may run within the same process. To add
' another service to this process, change the following line to
' create a second service object. For example,
'
' ServicesToRun = new System.ServiceProcess.ServiceBase[] {new Service1(), new MySecondUserService()};
'
ServicesToRun = New System.ServiceProcess.ServiceBase() {New AppScheduler()}
System.ServiceProcess.ServiceBase.Run(ServicesToRun)
End Sub 'Main
'/ <summary>
'/ Required method for Designer support - do not modify
'/ the contents of this method with the code editor.
'/ </summary>
Private Sub InitializeComponent()
'
' AppScheduler
'
Me.CanPauseAndContinue = True
Me.ServiceName = "Application Scheduler"
End Sub 'InitializeComponent
'/ <summary>
'/ Clean up any resources being used.
'/ </summary>
Protected Overrides Sub Dispose(disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub 'Dispose
'/ <summary>
'/ Set things in motion so your service can do its work.
'/ </summary>
Protected Overrides Sub OnStart(args() As String)
' TODO: Add code here to start your service.
configPath = ConfigurationSettings.AppSettings("configpath")
Try
Dim xRead As New XmlTextReader(configPath)
Dim xvRead As New XmlValidatingReader(xRead)
xvRead.ValidationType = ValidationType.DTD
dsTasks.ReadXml(xvRead)
xvRead.Close()
xRead.Close()
Catch Else
Dim srvcController As New ServiceController(ServiceName)
srvcController.Stop()
End Try
_timer.Interval = 30000
AddHandler _timer.Elapsed, AddressOf timeElapsed
_timer.Start()
End Sub 'OnStart
'/ <summary>
'/ Stop this service.
'/ </summary>
Protected Overrides Sub OnStop()
End Sub 'OnStop
End Class 'AppScheduler ' TODO: Add code here to perform any tear-down necessary to stop your service.
End Namespace 'AppScheduler
I have created a class named AppLauncher that accepts the executable name of a program as its constructor parameter. There is a method RunApp() in the class that creates a new ProcessInfo object with the specified path and calls Process.Start(ProcessInfo) with the ProcessInfo object as its parameter.
Class that launches applications on demand
Class AppLauncher
Private app2Launch As String
Public Sub New(ByVal path As String)
app2Launch = path
End Sub 'New
Public Sub runApp()
Dim pInfo As New ProcessStartInfo(app2Launch)
pInfo.WindowStyle = ProcessWindowStyle.Normal
Dim p As Process = Process.Start(pInfo)
End Sub 'runApp
End Class 'AppLauncher
I had to create a separate class to launch an application in a new thread, because the Thread class in .Net 2003 does not allow you to pass parameters to a thread delegate (whereas you can do so in .Net 2005). The ProcessStartInfo class can be used to create a new process. The static method Start (ProcessInfo) of the Process class returns a Process object that represents the process started.
There is a Timer variable used in the program, named _timer. The event handler for the timer's tick event is given below:
Event handler for the timer's tick event
Sub timeElapsed(sender As Object, args As ElapsedEventArgs)
Dim currTime As DateTime = DateTime.Now
Dim dRow As DataRow
For Each dRow In dsTasks.Tables("task").Rows
Dim runTime As DateTime = Convert.ToDateTime(dRow("time"))
Dim formatString As String = "MM/dd/yyyy HH:mm"
If(runTime.ToString(formatString)==currTime.ToString(formatString))Then
Dim exePath As String = dRow("exePath").ToString() Dim launcher As New AppLauncher(exePath)
New Thread(New ThreadStart(AddressOf launcher.runApp)).Start()
' Update the next run time
Dim strInterval As String = dRow("repeat").ToString().ToUpper()
Select Case strInterval
Case "D"
runTime = runTime.AddDays(1)
Case "W"
runTime = runTime.AddDays(7)
Case "M"
runTime = runTime.AddMonths(1)
End Select
dRow("time") = runTime.ToString(formatString)
dsTasks.AcceptChanges()
Dim sWrite As New StreamWriter(configPath)
Dim xWrite As New XmlTextWriter(sWrite)
dsTasks.WriteXml(xWrite, XmlWriteMode.WriteSchema)
xWrite.Close()
End If
Next dRow
End Sub 'timeElapsed
An easy way to compare date and time disregarding some particular values such as hour of the day or minute or second: convert them to the appropriate string format first, and check whether the two strings are equal. Otherwise, you have to individually check each item you want to compare, like If(currTime.Day==runtime.Day && currTime.Month==runtime.Month && ...). The interval values are : "D" (for daily schedule), "W" (for weekly schedule), and "M" (for monthly schedule). The values are read from an XML file named AppScheduler.xml. The file format is given below:
The XML file containing list of applications to launch
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE appSchedule[
<!ELEMENT appSchedule (task*)>
<!ELEMENT task EMPTY>
<!ATTLIST task name CDATA #REQUIRED>
<!ATTLIST task exePath CDATA #REQUIRED>
<!ATTLIST task time CDATA #REQUIRED>
<!ATTLIST task repeat (D|W|M) #REQUIRED>
<appSchedule>
<task name="Notepad" exePath="%SystemRoot%\system32\notepad.exe" time="05/05/2006 10:45" repeat="D"/>
<task name="Wordpad" exePath="C:\Program Files\Outlook Express\msimn.exe" time="05/05/2006 10:46" repeat="W"/>
<task name="Calculator" exePath="%SystemRoot%\System32\calc.exe" time="05/05/2006 10:47" repeat="M"/>
</appSchedule>
Starting the service
Protected Overrides Sub OnStart(args() As String)
' TODO: Add code here to start your service.
configPath = ConfigurationSettings.AppSettings("configpath")
Try
Dim xRead As New XmlTextReader(configPath)
Dim xvRead As New XmlValidatingReader(xRead)
xvRead.ValidationType = ValidationType.DTD
dsTasks.ReadXml(xvRead)
xvRead.Close()
xRead.Close()
Catch Else
Dim srvcController As New ServiceController(ServiceName)
srvcController.Stop()
End Try
_timer.Interval = 30000
AddHandler _timer.Elapsed, AddressOf timeElapsed
_timer.Start()
End Sub 'OnStart
The path of the XML file is set in the App.config file (the IDE will not create this file automatically, so you will have to manually add one into your project) in the following way:
App.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="configpath" value="C:\AppScheduler.xml"/>
</appSettings>
</configuration>
An XmlValidatingReader is used to ensure that the data strictly confirms to the DTD. The catch block stops the service, if some error occurs while trying to load data from the XML file. The timer interval is set to 30 seconds on starting the service.
To install/unistall the service
Build the application. Copy the AppScheduler.xml file to your C:\. Select Start > Programs > Microsoft Visual Studio .NET 2003 > Visual Studio .NET Tools > Visual Studio .NET 2003 Command Prompt. Go to the \bin\release folder in the project directory. Type the following command:
installutil AppScheduler.exe
Now, go to control panel. Select Performance and Maintenance > Administrative Tools and select Services. Doble-click on the AppScheduler service. Select the Log on tab. Check the Allow this service to interact with desktop checkbox. Click OK. Then click on the Start Service(}) button in the toolbar.
To uninstall the service, in the Visual Studio .NET command prompt, go to the \bin\release folder in the project directory and enter:
installutil /u AppScheduler.exe
Summary
Creating Windows services is fun, once you learn the basic things to do. XML is really a great tool that makes
lot simple to define data and behavior using plain text files.
NOTE: THIS ARTICLE IS CONVERTED FROM C# TO VB.NET USING A CONVERSION TOOL. ORIGINAL ARTICLE CAN BE FOUND ON C# CORNER (http://www.c-sharpcorner.com/).