Application Auto Update in VB.NET

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Introduction

This code enables an application to update itself when there is a new version available. The auto update is transparent to the user and checks for new updates every time the user launches the program. This code was written to be used in a controlled environment (intranet) and is not intended to be used through the internet due to security issues.

Background

I've been developing client/server systems for a long time, and the worst part of the software life cycle is to update it in all users' machine. The worst scenario is when you need to make a database change, and all the users are required have the latest version, otherwise the system will crash.

Today a lot of systems offer the ability to auto update, what makes the programmer's and the user's life easier. Looking through the internet, I couldn't find any code that I could use in my projects in a simple way, so I decided to write my own code.

Some points that I'd like to have in an auto update program are:

• Easy to implement and use.
• Transparent to the user.
• Ability to upgrade the system and also the auto update program.
• A code that doesn't need change when used by different systems and could be compiled in a library.

How it works

In the program that you want to be auto updateable, you just need to call the AutoUpdate function in the Main procedure. The AutoUpdate function will check the version with the one read from a file located in a web site. If the program version is lower than the one read the program downloads the auto update program and launches it and the function returns True, which means that an auto update will run and the current program should be closed. The auto update program receives several parameters from the program to be updated and performs the auto update necessary and after that launches the updated system.

The code

The auto update program

This is the code for the auto update program. The program is a windowless application with only one Main procedure. Here the only change that needs to be made is the error message at the end:

Imports System.IO
Imports System.Net

Module Main

    Public Sub Main()
        Dim ExeFile As String ' the program that called the auto update

        Dim RemoteUri As String ' the web location of the files

        Dim Files() As String ' the list of files to be updated

        Dim Key As String ' the key used by the program when called back 

                          ' to know that the program was launched by the 

                          ' Auto Update program

        Dim CommandLine As String ' the command line passed to the original 

                                  ' program if is the case

        Dim myWebClient As New WebClient ' the web client

        Try
            ' Get the parameters sent by the application

            Dim param() As String = Split(Microsoft.VisualBasic.Command(), "|")
            ExeFile = param(0)
            RemoteUri = param(1)
            ' the files to be updated should be separeted by "?"

            Files = Split(param(2), "?") 
            Key = param(3)
            CommandLine = param(4)
        Catch ex As Exception
            ' if the parameters wasn't right just terminate the program

            ' this will happen if the program wasn't called by the system 

            ' to be updated

            Exit Sub
        End Try
        Try
            ' Process each file 

            For i As Integer = 0 To Files.Length - 1
                Try
                    ' try to rename the current file before download the new one

                    ' this is a good procedure since the file can be in use

                    File.Move(Application.StartupPath & "\" & Files(i), _
                        Application.StartupPath & "\" & _
                        Now.TimeOfDay.TotalMilliseconds & ".old")
                Catch ex As Exception
                End Try
                ' download the new version
                myWebClient.DownloadFile(RemoteUri & Files(i), _
                    Application.StartupPath & "\" & Files(i))
            Next
            ' Call back the system with the original command line 
            ' with the key at the end
            System.Diagnostics.Process.Start(ExeFile, CommandLine & Key)
            ' do some clean up -  delete all .old files (if possible) 
            ' in the current directory
            ' if some file stays it will be cleaned next time
            Dim S As String = Dir(Application.StartupPath & "\*.old")
            Do While S <> ""
                Try
                    File.Delete(Application.StartupPath & "\" & S)
                Catch ex As Exception
                End Try
                S = Dir()
            Loop
        Catch ex As Exception
            ' something went wrong... 
            MsgBox("There was a problem runing the Auto Update." & vbCr & _
                "Please Contact [contact info]" & vbCr & ex.Message, _ 
                MsgBoxStyle.Critical)
        End Try
    End Sub
End Module

The auto update class/function

This is the class with the AutoUpdate function that checks if an update is needed. This can be directly copied to your code or can be in a library (DLL). If it's on your code, doesn't need to be a class.

This function receives a parameter by reference, the command line passed to the program, and can be the original command line or the one passed by the Auto Update program. If it was sent by the Auto Update program, the Key will be cleaned from the command line, so you must use the returned parameter instead of the original command line.

Here you need to change the RemotePath variable to point to your update web folder and the error message at the end:

Public Class AutoUpdate

    Public Function AutoUpdate(ByRef CommandLine As String) As Boolean
        Dim Key As String = "&**#@!" ' any unique sequence of characters

        ' the file with the update information

        Dim sfile As String = "update.dat" 
        ' the Assembly name 

        Dim AssemblyName As String = _
                System.Reflection.Assembly.GetEntryAssembly.GetName.Name
        ' here you need to change the web address 

        Dim RemotePath As String = _
            "http://[the web address for the update folder root]/"
        ' where are the files for a specific system

        Dim RemoteUri As String = RemotePath & AssemblyName & "/"

        ' clean up the command line getting rid of the key

        CommandLine = Replace(Microsoft.VisualBasic.Command(), Key, "")
        ' Verify if was called by the autoupdate

        If InStr(Microsoft.VisualBasic.Command(), Key) > 0 Then
            Try
                ' try to delete the AutoUpdate program, 

                ' since it is not needed anymore

                System.IO.File.Delete(_
                            Application.StartupPath & "\autoupdate.exe")
            Catch ex As Exception
            End Try
            ' return false means that no update is needed

            Return False
        Else
            ' was called by the user

            Dim ret As Boolean = False ' Default - no update needed

            Try
                Dim myWebClient As New System.Net.WebClient 'the webclient

                ' Download the update info file to the memory, 

                ' read and close the stream

                Dim file As New System.IO.StreamReader( _
                    myWebClient.OpenRead(RemoteUri & sfile))               
                Dim Contents As String = file.ReadToEnd()
                file.Close()
                ' if something was read

                If Contents <> "" Then
                    ' Break the contents 

                    Dim x() As String = Split(Contents, "|")
                    ' the first parameter is the version. if it's 

                    ' greater then the current version starts the 

                    ' update process

                    If x(0) > Application.ProductVersion Then
                        ' assembly the parameter to be passed to the auto 

                        ' update program

                        ' x(1) is the files that need to be 

                        ' updated separated by "?"

                        Dim arg As String = Application.ExecutablePath & "|" & _
                                    RemoteUri & "|" & x(1) & "|" & Key & "|" & _
                                    Microsoft.VisualBasic.Command()
                        ' Download the auto update program to the application 

                        ' path, so you always have the last version runing

                        myWebClient.DownloadFile(RemotePath & "autoupdate.exe", _
                            Application.StartupPath & "\autoupdate.exe")
                        ' Call the auto update program with all the parameters

                        System.Diagnostics.Process.Start( _
                            Application.StartupPath & "\autoupdate.exe", arg)
                        ' return true - auto update in progress

                        ret = True 
                    End If
                End If
            Catch ex As Exception
                ' if there is an error return true, 

                ' what means that the application

                ' should be closed

                ret = True 
                ' something went wrong... 

                MsgBox("There was a problem runing the Auto Update." & vbCr & _
                    "Please Contact [contact info]" & vbCr & ex.Message, _
                    MsgBoxStyle.Critical)
            End Try
            Return ret
        End If
    End Function
End Class

The auto update web folder

The auto update web folder should have a folder for each system you want to upgrade. The root folder is the one that you will refer on the RemotePath variable. The AutoUpdate.exe program should be on this folder. Each subfolder should be named as the assembly name (normally the program name without the extension). Inside the program folder you save the files that you want to update and the file update.dat with the last file version and the files that you want to update. The first parameter is the version and the second parameter separated by a "|" are the files that you want to update, which are separated by "?" as follows:

1.2.1234.5543|MyProgram.exe?file1.txt?file2.cfg

Using the code

Well, now to use the code is very simple. In the application where you want to enable the auto update, just call the AutoUpdate function. You must declare a variable CommandLine that will hold the arguments passed to the program and use it, if you need, instead of the Microsoft.VisualBasic.Command() function.

    ' The variable with the command line (to replace the 

    ' Microsoft.VisualBasic.Command() function)

    Public CommandLine As String

    Public Sub Main()
        ' if you are using class create it

        Dim MyAutoUpdate As New AutoUpdate        
        ' test if an update is needed and quit the program if so.    

        If MyAutoUpdate.AutoUpdate(CommandLine) Then Exit Sub
        ' here goes your regular code in the main sub

    End Sub

Points of interest

This auto update was written with the intention to always check for a new version, since the application involved can have problems if it runs in an old version. It guarantees that everyone who is using the application is running the latest version. This can be easily changed to update if something is available but don�t crash if it�s not.

This program works fine for small sized programs and a few files. If you need to download large files I suggest you to open a splash screen and give a message to the user that something is happening.

Limitations

• The original command line can't have the character "|", since it is used as a delimiter in the Auto Update program.
• The user must have permission to write files in the application install folder.
• The main program should use the variable CommandLine instead of the original command line, since it can have the key attached to it.