Async HTTP POST to download binary file

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I am trying to download files in VB 2005 Asynchronously (To avoid UI JAM) , I need to HTTP POST the filename to the server and the file is being supplied as server response. Pls. guide. This is what I am currrently using but its OK only for Text, Html files. Tried code below but it corrupts binary files.

Public Sub PostData(ByVal strURL As String, Optional ByVal POST1  As String = "") 
 
 
 
        ' Declare a variable named client of type WebClient. 
 
        Dim myWebClient As WebClient 
 
        ' Instantiate a WebClient object and assign it to the 'client' variable. 
 
        myWebClient = New WebClient 
 
 
 
        ' Add handler to process theWebClient's DownloadProgressChanged events. 
 
        AddHandler myWebClient.UploadProgressChanged, AddressOf UploadProgress 
 
 
 
        ' Add handler to process theWebClient's DownloadCompleted event. 
 
        AddHandler myWebClient.UploadStringCompleted, AddressOf UploadCompleted 
 
 
 
        ' Declare a variable named downloadUri of type Uri 
 
        Dim downloadUri As Uri 
 
        ' Instantiate a new Uri object and assign it to the 'downloadUri' variable. 
 
        downloadUri = New Uri(strURL) 
 
 
 
        myWebClient.Headers.Add("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4") 
 
        'myWebClient.Headers.Add("Accept-Language", "en-us,en;q=0.5") 
 
 
 
        Try 
 
             
 
            
 
                myWebClient.UploadStringAsync(downloadUri, "filename=" &POST1) 
 
            End If 
 
 
 
        Catch e As System.Net.WebException 
 
            MsgBox("A web exception has occured [" & strURL & "]." & vbCrLf & " System returned: " & e.Message, MsgBoxStyle.Exclamation, "Error!") 
 
            Exit Try 
 
 
 
        Catch e As System.Net.ProtocolViolationException 
 
            MsgBox("A protocol violation has occured [" & strURL & "]." & vbCrLf & "  System returned: " & e.Message, MsgBoxStyle.Exclamation, "Error!") 
 
            Exit Try 
 
 
 
        Catch e As System.Net.Sockets.SocketException 
 
            MsgBox("Socket error [" & strURL & "]." & vbCrLf & "  System returned: " & e.Message, MsgBoxStyle.Exclamation, "Error!") 
 
            Exit Try 
 
 
 
        Catch e As System.IO.EndOfStreamException 
 
            MsgBox("An IO stream exception has occured. System returned: " & e.Message, MsgBoxStyle.Exclamation, "Error!") 
 
            Exit Try 
 
 
 
        End Try