VB.NET Checking for remote file

[johnd60]

Hi there,

First-time poster but long-time lurker.

I've been working on an application in VB.NET which will serve as a web-installer on a client machine, looking locally for files on a list downloaded from the server, checking their versions against server versions, and downloading updates where necessary, via HTTP or FTP. It's all going remarkably well so far and I've found VB very easy to pick up.

Where I've had trouble is in a function to check whether or not a file exists on the repository; essentially, that is, to check whether http://domain.com/path/to/file.ext is valid. I've found various different ways of checking for files on a local machine, and several for checking on local-network servers (I believe - all of the paths were \\server\path\to\file.ext or similar).

Finally, I'd be averse to (but not entirely against) bundling up a C# dll or similar. If that's the only way, then I'd still really appreciate a helping hand with the code, but if there's any chance of doing this in VB (even if it is more complex), I'd much rather be able to make the whole thing into one standalone executable.

Thanks very much in advance

John

[johnd60]

Well, after some more searching, I've found a way to do this; rather obvious and I'm surprised I didn't think of it before.

Essentially, the code creates a web request for the file:

Private Sub Button1_Click() Handles Button1.Click
  Dim request As HttpWebRequest = CType(WebRequest.Create(http://domain.com/path/to/file.xtn), HttpWebRequest)
  Try
    Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
    MessageBox.Show("File Found") ' will only be processed if request successful
  Catch ex As WebException
    If ex.Status <> WebExceptionStatus.Success Then
      MessageBox.Show("Errors")
    End If
  End Try
End Sub

For anyone who wants to use this code, I suggest altering the processing of ex.Status to take account of the various different WebExceptionStatus values, which can be found here: http://technet.microsoft.com/en-us/l...ionstatus.aspx. This will allow you to supply more specific error messages based on the actual error encountered; for me, the above is all I need.

Hope someone else finds this useful too!


Yours

John