如何使我的应用程序在启动时检查更新，然后下载？

Question

我尝试过：

Dim address As String = "http:/test/updateConfirm.txt"
     Dim client As WebClient = New WebClient()
     Dim updateConfirmVar As String = client.DownloadString(address)
     If updateConfirmVar = "available" Then

但是我想用clickOnce更新系统来做。怎么做？