How to use HttpWebRequest to download file

问题:

Trying to download file in code.

Current code:

  Dim uri As New UriBuilder
    uri.UserName = "xxx"
    uri.Password = "xxx"
    uri.Host = "xxx"
    uri.Path = "xxx.aspx?q=65"

   Dim request As HttpWebRequest = DirectCast(WebRequest.Create(uri.Uri), HttpWebRequest)

    request.AllowAutoRedirect = True

    request = DirectCast(WebRequest.Create(DownloadUrlIn), HttpWebRequest)
    request.Timeout = 10000
    'request.AllowWriteStreamBuffering = True

    Dim response As HttpWebResponse = Nothing
    response = DirectCast(request.GetResponse(), HttpWebResponse)
    Dim s As Stream = response.GetResponseStream()

    'Write to disk
    Dim fs As New FileStream("c:\xxx.pdf", FileMode.Create)

    Dim read As Byte() = New Byte(255) {}
    Dim count As Integer = s.Read(read, 0, read.Length)
    While count > 0
        fs.Write(read, 0, count)
        count = s.Read(read, 0, read.Length)
    End While

    'Close everything
    fs.Close()
    s.Close()
    response.Close()

Running this code and checking the response.ResponseUri indicates im being redirected back to the login page and not to the pdf file.

For some reason its not authorising access what could I be missing as Im sending the user name and password in the uri? Thanks for your help

回答1:

You don't need all of that code to download a file from the net just use the WebClient class and its DownloadFile method

回答2:

you should check and see if the site requires cookies (most do), i'd use a packet analyzer and run your code and see exactly what the server is returning. use fiddler or http analyzer to log packets

回答3:

With UWP, this has become a more pertinent question as UWP does not have a WebClient. The correct answer to this question is if you are being re-directed to the login page, then there must be an issue with your credentials OR the setting (or lack of) header for the HttpWebRequest.

According to Microsoft, the request for downloading is sent with the call to GetResponse() on the HttpWebRequest, therefore the downloaded file SHOULD be in the stream in the response (returned by the GetResponse() call mentioned above).