vb.net 2005, threading file locking issue, I think - vb.net

Question

I'm using vb.net 2005, I've got the following code running a thread to download a file. However, the process fails sometimes when trying to read the local copy of the file. I think I may need to unlock the local file somehow but I'm not sure how to do this. Can someone take a look and advise me ?
Dim BP1Ended As Boolean = False
Private Sub BackgroundProcess1()
BP1Ended = False
mPadFileStatus = DownloadFile(mstrPadUrl, mLocalFile)
BP1Ended = True
End Sub
'---'
Dim t As System.Threading.Thread
t = New System.Threading.Thread(AddressOf BackgroundProcess1)
t.Start()
Dim ProcessStartTime As Date = Now()
Do While ProcessStartTime.AddMinutes(1) >= Date.Now
Application.DoEvents()
If BP1Ended = True Then
Exit Do
End If
Loop
t.Abort()
PadFileStatus = mPadFileStatus
If BP1Ended = False Then
Application.DoEvents()
AddConsoleMsg("Downloading file.... Aborted", True)
End If
'---'
Public Function DownloadFile(ByVal pstrRequestedFile As String, ByVal pstrDestinationFile As String, Optional ByVal TimeOut As Integer = 120) As DownloadStatus
Dim input As IO.Stream
Dim Req As System.Net.HttpWebRequest = Nothing
Dim Response As System.Net.HttpWebResponse
Try
Req = System.Net.HttpWebRequest.Create(pstrRequestedFile)
Catch ex As Exception
Return DownloadStatus.UnknownError
End Try
Req.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"
Req.Timeout = TimeOut * 1000 '120 * 1000 '1 second = 1 000 milliseconds
Try
Response = Req.GetResponse
input = Response.GetResponseStream
Dim streamreader As New StreamReader(input, System.Text.Encoding.GetEncoding("windows-1252")) 'System.Text.Encoding.UTF8)'
Dim s_response As String = streamreader.ReadToEnd()
streamreader.Close()
Dim filestream As New FileStream(pstrDestinationFile, FileMode.Create)
Dim streamwriter As New StreamWriter(filestream, System.Text.Encoding.GetEncoding("windows-1252")) ' System.Text.Encoding.UTF8)'
streamwriter.Write(s_response)
streamwriter.Flush()
streamwriter.Close()
Dim length As Long = 1000000 * 100
Dim pos As Long = 0
If Response.ContentLength > 0 Then
length = Response.ContentLength
End If
If length > 0 Then
Return DownloadStatus.OK
End If
input.Close()
Catch ew As System.Net.WebException
If ew.Status = WebExceptionStatus.NameResolutionFailure Or ew.Status = WebExceptionStatus.ProtocolError Then
Return DownloadStatus.FileNotFound
ElseIf ew.Status <> WebExceptionStatus.Success Then
Return DownloadStatus.UnknownError
End If
'Dim errorRespone As HttpWebResponse = CType(ew.Response, HttpWebResponse)
'If errorRespone.StatusCode = HttpStatusCode.NotFound Then '404
' Return DownloadStatus.FileNotFound
'Else
' Return DownloadStatus.UnknownError
'End If'
Catch ex As Exception 'Don't know'
Return DownloadStatus.UnknownError
End Try
End Function
'---'
Dim OpenFile As FileStream
'OpenFile = New FileStream(pstrPadFile, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)
'FAILS HERE
OpenFile = New FileStream(pstrPadFile, FileMode.Open, FileAccess.Read, FileShare.Read)

Answer 1

You don't close the file stream in case of exception which might lead to the lock. Make sure you always dispose disposable resources by wrapping them in Using statements:
Using filestream As FileStream = New FileStream(pstrDestinationFile, FileMode.Create)
Using streamwriter As StreamWriter = New StreamWriter(filestream, Encoding.GetEncoding("windows-1252"))
streamwriter.Write(s_response)
End Using
End Using
Same stands true for the response and response streams. They should be properly disposed.
Also you may consider using the WebClient class which has methods like DownloadFile and DownloadData which could make your life much easier.