Vb.net not closing file after reading from it - windows

Question

When refreshing my application, I have to read from a text file which has information stored in it. After it is read I make sure I have closed it 'file.close()' the next time I refresh the applicaztion the text file should be generated again and overright the previous one.
The problem is that it cant change the file because it is aparantly in use by another process but as soon as I close my application it works fine. Is there anyway to stop the process before refreshing it so it works correctly? The text file is called NetworkInfo.txt.
Thanks
Chris
EDIT
Every time I refresh the application I run a batch file that generates a file with all the network info in. (IPConfig/all)
I then have a module that reads from it like the following:
Public Function EthDefaultGateway() As String
Dim sr As New System.IO.StreamReader(ipconfig)
Try
Dim foundEthernet As Boolean = False
Dim gateway As String = ""
Do Until sr.EndOfStream
Dim line As String = sr.ReadLine()
If line.Contains("Ethernet adapter LAN:") OrElse line.Contains("Ethernet adapter Local Area Connection:") Then
foundEthernet = True
End If
If foundEthernet Then
If line.Contains("Default Gateway . . . . . . . . . :") Then
gateway = line.Substring(line.IndexOf(":") + 1).Trim
Exit Do
End If
End If
Loop
If gateway = "" Then
gateway = "Unknown"
End If
If gateway = "::" Then
gateway = "Unknown"
End If
Return gateway
Catch ex As Exception
EthDefaultGateway = "Unknown"
End Try
sr.Close()
sr.Dispose()
End Function
From this I gather all the bits of information I need. (There probs is a lot better way of doing this but Im only a nooby and I cant find any other ideas on here, the web or from friends.)
All of these close the file after readinf from it (sr.close)
Some reason though its not closing it. The only other thing It could be is the batch file isnt closing it which I think is very unlikely
The problem is that when I change the IP or refresh the form it fails because the batch file cannot over write the network info file.
Any suggestions?
I was just thinking of a way to kill the process after the refresh but I didnt know if this was a good idea or if it was doable or how to do it tbh.

Answer 1

Return gateway
That bypasses the sr.Close() call at the bottom. So the file won't be closed. Always favor using the Using statement so it is automatic and can't be forgotten or skipped or bypassed because of an exception:
Public Function EthDefaultGateway() As String
Using sr As New System.IO.StreamReader(ipconfig)
'' Rest of your code
End Using
End Function