Question

我用它来下载附件，文件正在下载但原始内容不存在，内容只显示为System.Byte[]

Protected Sub DownloadFile(ByVal sender As Object, ByVal e As EventArgs)

    Dim id As Integer = Integer.Parse(TryCast(sender, LinkButton).CommandArgument)
    Dim bytes As Byte()
    Dim fileName As String, contentType As String
    strQry = "select file_name, license_doc, file_type from Driver_Mas where Id=" & Val(id)

    Reader = Osql.ExecuteRead(strQry)
    While Reader.Read

        bytes = Encoding.UTF8.GetBytes(Reader.Item("license_doc"))

        contentType = Reader.Item("file_type").ToString()
        fileName = Reader.Item("file_name").ToString()



        Response.Clear()
        Response.Buffer = True
        Response.Charset = ""
        Response.Cache.SetCacheability(HttpCacheability.NoCache)
        Response.ContentType = contentType
        Response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName)
        Response.BinaryWrite(bytes)
        Response.Flush()
        Response.End()
    End While
End Sub

Answer 1

以下代码从文件名中获取mimetype，coudl要好得多，这应该可以帮到你。

Private Sub ShowDocument(fileName As String, fileContent As Byte())
    'Split the string by character . to get file extension type
    Dim stringParts As String() = fileName.Split(New Char() {"."C})
    Dim strType As String = stringParts(1)
    Response.Clear()
    Response.ClearContent()
    Response.ClearHeaders()
    Response.AddHeader("content-disposition", Convert.ToString("attachment; filename=") & fileName)
    'Set the content type as file extension type
    Response.ContentType = strType
    'Write the file content
    Me.Response.BinaryWrite(fileContent)
    Me.Response.End()

End Sub

Answer 2

你可能想要一些更健壮的东西。这是我在尝试将任意文件发送到浏览器时使用的代码。您应该只需调用WriteFile方法，提供数据。请注意，内容类型取决于您。我们使用“application / octet-stream”强制浏览器只想保存文件，而不是直接在浏览器中打开它。

''' <summary>
''' Writes HTTP headers to support the transfer of a physical data file
''' </summary>
''' <param name="incomingFilename"></param>
''' <param name="fileLength"></param>
''' <param name="response"></param>
''' <param name="contentType"></param>
''' <remarks></remarks>
Public Shared Sub WriteFileResponseHeaders(incomingFilename As String, fileLength As Integer?, response As System.Web.HttpResponse, contentType As String)
    For Each c As Char In System.IO.Path.GetInvalidFileNameChars
        incomingFilename = incomingFilename.Replace(c, "-"c)
    Next

    'Strip disallowed characters from the filename
    Dim SafeName As String = incomingFilename
    Dim BadChars As String = "!@#$%^&*():<>?,/;"""

    For i As Integer = 0 To BadChars.Length - 1
        SafeName = SafeName.Replace(BadChars.Substring(i, 1), String.Empty)
    Next

    Dim EncodedUtf As String = "utf-8''"

    BadChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!#$&+=.^_'|~"

    For i As Integer = 0 To incomingFilename.Length - 1
        If BadChars.IndexOf(incomingFilename.Chars(i)) > -1 Then
            EncodedUtf &= incomingFilename.Chars(i)
        Else
            EncodedUtf &= "%" & AscW(incomingFilename.Chars(i)).ToString("x")
        End If
    Next

    With response
        .Clear()
        .ClearContent()
        .ClearHeaders()

        .AppendHeader("content-type", contentType)
        .AppendHeader("content-disposition",
                             String.Format("attachment; filename*={0}; size={1}; creation-date={2}; modification-date={2};read-date={2}; filename=""{3}""",
                                           EncodedUtf, If(fileLength.HasValue, fileLength, 0), Date.Now.ToString("R").Replace(",", " "), SafeName))


    End With
End Sub

Public Shared Sub WriteFile(fileData() As Byte, saveAs As String, response As System.Web.HttpResponse, contentType As String)
    WriteFileResponseHeaders(saveAs, fileData.Length, response, contentType)

    response.OutputStream.Write(fileData, 0, fileData.Length)
    response.Flush()
End Sub

下载附件

2 个答案: