Help with replacing an already running dll

Imports System.Net
Imports System.IO
Imports System.Text
 
Public Class Form1
 
    Private appPath As String = "C:\Program Files\Your Application Path\"
    Private appExecutable As String = "application.exe"
    Private updateVersionURL As String = "http://update.yoursite.com/version.php"
    Private updateFileListURL As String = "http://update.yoursite.com/update.php"
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    End Sub
 
    Private Sub tmrAsync_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrAsync.Tick
        ' Using a timer is a hack to allow asynchronous code execution without the need
        ' to use delegate invocation to perform cross-thread operations. It also eliminates
        ' the need to gain exclusive access to objects using such classes as Monitor.
        tmrAsync.Enabled = False
        CheckUpdate()
    End Sub
 
    Private Sub CheckUpdate()
        lstLog.Items.Add("Checking for new version...")
        Application.DoEvents()
        Dim wc As New WebClient
        ' Grab the latest version info in format "<major>.<minor>.<build>" e.g. 4.2.1335
        Dim latestVersion As String = wc.DownloadString(updateVersionURL)
        ' Get the file version of your current EXE
        Dim fv As FileVersionInfo = FileVersionInfo.GetVersionInfo(appPath & appExecutable)
        Dim fvs As String = fv.ProductMajorPart & "." & fv.ProductMinorPart & "." & fv.ProductBuildPart
        If fvs <> latestVersion Then
            lstLog.Items.Add("New version found!")
            ' Update is available, ask the user
            If MessageBox.Show("There is a new version (" & latestVersion & "). Do you want to update?", "Update", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.No Then
                wc.Dispose()
                Application.Exit()
                Exit Sub
            End If
            ' Get the list of files to download
            ' The download URLs should be one per line, the local path preceeds them
            ' delimited by a | character. For example:
            ' application.exe|http://update.yoursite.com/files/application.exe
            ' path\to\mylib.dll|http://update.yoursite.com/files/mylib.dll
            Dim updateParts As String = wc.DownloadString(updateFileListURL)
            ' Create a stream reader for the update info
            Dim sr As New StreamReader(New MemoryStream(UTF8Encoding.UTF8.GetBytes(updateParts)))
            ' Go through the update URLs and download each one to the specified path
            Do
                Dim l As String = sr.ReadLine()
                Dim lp() As String = Split(l, "|")
                ' lp(0) is the path, lp(1) is the URL
                lstLog.Items.Add("Updating " & lp(0))
                Application.DoEvents()
                ' Download the file and overwrite the old one
                wc.DownloadFile(lp(1), appPath & lp(1))
                Application.DoEvents()
            Loop While Not sr.EndOfStream
            MessageBox.Show("Patching complete!", "Update")
        Else
            lstLog.Items.Add("No later version found.")
            MessageBox.Show("The application is up to date.", "Update")
        End If
        wc.Dispose()
        Application.Exit()
    End Sub
End Class

                                              

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