asked on

Update form progress bar from within class

I am using the Microsoft FTP class to carry out some ftp functions. when I use the download function of the class I would like to be able to update a progress bar on the current form. As I will call the class from many different forms I am not sure how to handle this as when the download function is called the program does not hand back control to the form until the download has completed.

I have included a copy of the relevant MS download subprocedure that is called from my windows form

500 points for a working solution.

Public Sub DownloadFile(ByVal sFileName As String, _
ByVal sLocalFileName As String, _
ByVal bResume As Boolean)
Dim st As Stream
Dim output As FileStream
Dim cSocket As Socket
Dim offset, npos As Long

If (Not (m_bLoggedIn)) Then
Login()
End If

SetBinaryMode(True)

If (sLocalFileName.Equals("")) Then
sLocalFileName = sFileName
End If

If (Not (File.Exists(sLocalFileName))) Then
st = File.Create(sLocalFileName)
st.Close()
End If

output = New FileStream(sLocalFileName, FileMode.Open)
cSocket = CreateDataSocket()
offset = 0

If (bResume) Then
offset = output.Length

If (offset > 0) Then
'Send an FTP command to restart.
SendCommand("REST " & offset)
If (m_iRetValue <> 350) Then
offset = 0
End If
End If

If (offset > 0) Then
npos = output.Seek(offset, SeekOrigin.Begin)
End If
End If
'Send an FTP command to retrieve a file.
SendCommand("RETR " & sFileName)

If (Not (m_iRetValue = 150 Or m_iRetValue = 125)) Then
output.Close()
MessageString = m_sReply
Throw New IOException(m_sReply.Substring(4))
End If

Do While (True)
m_aBuffer.Clear(m_aBuffer, 0, m_aBuffer.Length)
m_iBytes = cSocket.Receive(m_aBuffer, m_aBuffer.Length, 0)
output.Write(m_aBuffer, 0, m_iBytes)

If (m_iBytes <= 0) Then
Exit Do
End If
Loop

output.Close()
If (cSocket.Connected) Then
cSocket.Close()
End If

ReadReply()
If (Not (m_iRetValue = 226 Or m_iRetValue = 250)) Then
MessageString = m_sReply
Throw New IOException(m_sReply.Substring(4))
End If

End Sub

Mikal613

using api

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/commctls/progbar/progbar.asp

you can do that

shawl01

ASKER

I would prefer to use my own form as it has other info on it as well and is already loaded and displaying on screen at the point where the ftp download is called. I want to achieve this within vb.net

Is their not some way of referencing a calling forms controls to update them and then update the on-screen display ?

Mikal613

so add a progress bar ro your form and make a public sub

Public Sub UpdateProgressBar()
ProgressBar1.value = ProgressBar1.value + 1
end sub

and call that function from within your class

Carl Tawn

If you have the code for the class (or can inherit from it) you could add an Event to the class that fires at intervals during the transfer, and then subscribe ot the event from your form to handle updating the progress bar.

shawl01

ASKER

carl tawn

Can you give any more details on this and maybe an example
I am not sure what you mean when you say subscribe to an event

Thanks

Carl Tawn

Say, for example, that your FTP class had an event called Transferring that fired every so often during the transfer and in your form you created an object like:

Public Sub Form_Load()

Dim obj As New YourFTPClass()
AddHandler obj.Transferring, AddressOf UpdateProgressBar

End Sub

Public Sub UpdateProgressBar()

'// This sub will be called everytime the Transferring event is fired by the YourFTPClass object

End Sub

shawl01

ASKER

Can you tell me how to define the event? I thought I knew but after a bit of reading I am now more confused

Sorry to be a pain
Thanks

ASKER CERTIFIED SOLUTION

Carl Tawn

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Mikal613

so add a progress bar ro your form and make a public sub

Public Sub UpdateProgressBar()
ProgressBar1.value = ProgressBar1.value + 1
end sub

and call that function from within your class

Carl Tawn

The problem with that method is that the FTP clas then becomes tied to a specific form, or at least a form with an UpdateProgressBar method. By using events instead you allow the FTP class to notify consumers when something happens, and it is up to the Form (or whatever object is using the FTP class) whether they want to know about it or not.

Mikal613

he just wants to update a form. Its simple

shawl01

ASKER

carl tawn
Many thanks your solution worked, I managed to define two events 1) Initialise the progress bar 2) Increment the progress bar passing through the additional bytes downloaded. I can also use this from different forms without any additional coding.

Mika613
carl tawn is correct in what he is saying about tying to a specific form, if you check my initial question you will see that I said I would be calling it from different forms.

Many thanks to both for your suggestions.
I will award the points to carl tawn.