How to upload files to a Web server by using ASP

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For a Microsoft Visual Basic .NET version of this article, see 315832.


This article describes how to enable your Web server to receive file transfers from Microsoft Active Server Pages (ASP) pages by using a server-side Microsoft COM+ component.

NOTE: Microsoft Support boundaries for Visual Basic 6 development have changed. For more information, please see


  1. Microsoft Windows 2000 with Microsoft Internet Information Server 5.0 (IIS) installed and configured
  2. If your development computer is a different computer than the server, you must have a valid network or Internet connection to the server that hosts the ASP pages.

Microsoft Visual Basic 6 Project Setup and Code

  1. Start Visual Basic, and then start a new ActiveX DLL project.
  2. Name the project ASPFileUpload.
  3. Change the name of Class1 to File.
  4. On the Project menu, click References.
  5. In the References dialog box, click to select the following options, and then click OK:
    • Visual Basic For Applications
    • Visual Basic runtime objects and procedures
    • Visual Basic objects and procedures
    • OLE Automation
    • COM+ Services Type Library
    • Microsoft Active Server Pages Object Library
    • Microsoft Scripting Runtime
  6. On the Project menu, click ASPFileUpload Properties.
  7. In the Project Properties dialog box, click to select Unattended Execution and Retained In Memory, and then click OK.
  8. Paste the following code to File.cls:
    Option Explicit
    Const ERR_INVALID_FILENAME = vbObjectError + 1000
    Const ERR_INVALID_TARGET = vbObjectError + 1001
    Const ERR_FILE_EXISTS = vbObjectError + 1002
    Const ERR_UPLOAD_CALLED = vbObjectError + 1003
    Const VB_ERR_PATH_NOT_FOUND = 76
    Private m_objContext As ObjectContext
    Private m_objRequest As ASPTypeLibrary.Request
    Private m_strTarget As String
    Private m_strFileName As String
    Private m_blnOverWrite As Boolean
    Private m_blnUploaded As Boolean
    Private m_lngTotalBytes As Long
    'All other form elements go here.
    Private m_formCol As Scripting.Dictionary
    Implements ObjectControl
    Private Function ObjectControl_CanBePooled() As Boolean
      ObjectControl_CanBePooled = False
    End Function
    Private Sub ObjectControl_Activate()
      Set m_objContext = GetObjectContext()
      Set m_objRequest = m_objContext("Request")
      Set m_formCol = New Scripting.Dictionary
    End Sub
    Private Sub ObjectControl_Deactivate()
      Set m_objContext = Nothing
      Set m_objRequest = Nothing
      Set m_formCol = Nothing
    End Sub
    Public Sub Upload()
      Const DEFAULT_CHUNK_SIZE = 262144 '256kb
      Dim bytBeginOfChunk() As Byte
      Dim bytEndOfChunk() As Byte
      Dim bytBeginOfName() As Byte
      Dim bytEndOfName() As Byte
      Dim bytBeginOfFile() As Byte
      Dim bytEndOfFile() As Byte
      Dim bytBeginOfValue() As Byte
      Dim bytEndOfValue() As Byte
      Dim bytName() As Byte
      Dim bytValue() As Byte
      Dim bytThisChunk() As Byte
      Dim bytFileName() As Byte
      Dim lngBeginOfChunk As Long
      Dim lngEndOfChunk As Long
      Dim lngBeginOfAttribute As Long
      Dim lngEndOfAttribute As Long
      Dim lngBeginOfValue As Long
      Dim lngEndOfValue As Long
      Dim blnEndOfData As Boolean
      Dim lngChunkSize As Long
      Dim lngBytesLeft As Long
      Dim lngFileNum As Long
      Dim strFileName As String
      On Error GoTo UploadErr
      If Uploaded Then
        Err.Raise ERR_UPLOAD_CALLED, App.Title, "The Upload method has already been called."
      End If
      bytBeginOfChunk = StrConv("-----------------------------", vbFromUnicode)
      bytEndOfChunk = StrConv("-----------------------------", vbFromUnicode)
      bytBeginOfName = StrConv("name=", vbFromUnicode) & ChrB(34)
      bytEndOfName = ChrB(34)
      bytBeginOfFile = StrConv("filename=", vbFromUnicode) & ChrB(34)
      bytEndOfFile = ChrB(34)
      bytBeginOfValue = ChrB(13) & ChrB(10) & ChrB(13) & ChrB(10)
      bytEndOfValue = ChrB(13) & ChrB(10) & StrConv("-----------------------------", vbFromUnicode)
      'Initialize the chunk size.
      If m_objRequest.TotalBytes <= DEFAULT_CHUNK_SIZE Then
        lngChunkSize = m_objRequest.TotalBytes
        lngChunkSize = DEFAULT_CHUNK_SIZE
      End If
      'Get the chunk from the request object.
      bytThisChunk = m_objRequest.BinaryRead(CVar(lngChunkSize))
      'Initialize the value.
      lngBeginOfChunk = 1
      'Repeat until the end of the data.
      Do While Not blnEndOfData
        'Begin the chunk.
        lngBeginOfChunk = InStrB(lngBeginOfChunk, bytThisChunk, bytBeginOfChunk) + UBound(bytBeginOfChunk)
        'Get name of the item.
        lngBeginOfAttribute = InStrB(lngBeginOfChunk, bytThisChunk, bytBeginOfName) + UBound(bytBeginOfName) + 1
        lngEndOfAttribute = InStrB(lngBeginOfAttribute, bytThisChunk, bytEndOfName)
        bytName = MidB(bytThisChunk, lngBeginOfAttribute, lngEndOfAttribute - lngBeginOfAttribute)
        'Get the value of the item.
        lngBeginOfValue = InStrB(lngEndOfAttribute, bytThisChunk, bytBeginOfValue, vbBinaryCompare) + UBound(bytBeginOfValue) + 1
        lngEndOfValue = InStrB(lngBeginOfValue, bytThisChunk, bytEndOfValue, vbBinaryCompare)
        If lngEndOfValue = 0 Then
          'The item extends the past current chunk.
          bytValue = MidB(bytThisChunk, lngBeginOfValue, lngChunkSize)
          'The item value exists in the current chunk.
          bytValue = MidB(bytThisChunk, lngBeginOfValue, lngEndOfValue - lngBeginOfValue)
        End If
        If UCase(StrConv(bytName, vbUnicode)) = "FILE" Then
          lngBeginOfAttribute = InStrB(lngBeginOfChunk, bytThisChunk, bytBeginOfFile, vbBinaryCompare) + UBound(bytBeginOfFile) + 1
          lngEndOfAttribute = InStrB(lngBeginOfAttribute, bytThisChunk, bytEndOfFile, vbBinaryCompare)
          bytFileName = MidB(bytThisChunk, lngBeginOfAttribute, lngEndOfAttribute - lngBeginOfAttribute)
          If UBound(bytFileName) < 0 Or UBound(bytValue) < 0 Then
            Err.Raise ERR_INVALID_FILENAME, App.Title, "Invalid File Name."
          End If
          If Me.Target = "" Then
            Err.Raise ERR_INVALID_TARGET, App.Title, "Invalid Target."
          End If
          'Use the original file name.
          If Me.FileName = "" Then
            'Trim the path from the file name.
            While InStrB(1, bytFileName, StrConv("\", vbFromUnicode), vbBinaryCompare) > 0
              bytFileName = MidB(bytFileName, InStrB(1, bytFileName, StrConv("\", vbFromUnicode)) + 1)
            'Set the property.
            Me.FileName = StrConv(bytFileName, vbUnicode)
            'Convert the byte to Unicode.
            strFileName = Me.Target & Me.FileName
            strFileName = Me.Target & Me.FileName
          End If
          'Check for overwrite.
          If Me.OverWrite Then
            'This is the hack check. Make sure that wildcard characters cannot be used.
            If Not InStr(1, strFileName, "*") Then
              If FileExists(strFileName) Then
                Kill strFileName
              End If
              Err.Raise ERR_INVALID_FILENAME, App.Title, "The specified file name appears to be invalid."
            End If
            If FileExists(strFileName) Then
              Err.Raise ERR_FILE_EXISTS, App.Title, "The file already exists."
            End If
          End If
          lngFileNum = FreeFile
          Open strFileName For Binary Access Write As #lngFileNum
          'Write the file to the destination directory.
          Put #lngFileNum, , bytValue
          'This chunk is empty. Therefore, get a new chunk.
          lngBytesLeft = m_objRequest.TotalBytes - lngChunkSize
          'Start the chunking machine.
          Do While lngBytesLeft > 0
            'Get a new chunk.
            bytThisChunk = m_objRequest.BinaryRead(CVar(lngChunkSize))
              lngEndOfValue = InStrB(1, bytThisChunk, bytEndOfValue, vbBinaryCompare)
              If lngEndOfValue > 0 Then
                'The item value exists in the current chunk.
                bytThisChunk = MidB(bytThisChunk, 1, lngEndOfValue - 1)
              End If
              'Append the chunk to the file.
              Put #lngFileNum, , bytThisChunk
              lngBytesLeft = lngBytesLeft - lngChunkSize
              If lngBytesLeft < lngChunkSize Then
                lngChunkSize = lngBytesLeft
              End If
            Close #lngFileNum
            TotalBytes = FileLen(strFileName)
         ' Exit Do
          If UCase(StrConv(bytName, vbUnicode)) = "SAVEAS" Then
           Me.FileName = StrConv(bytValue, vbUnicode)
           'form field other than file, such as textboxes 
           If UBound(bytValue) > 0 And UBound(bytName) > 0 Then 
            m_formCol.Add StrConv(bytName, vbUnicode), StrConv(bytValue, vbUnicode)
            m_formCol.Add StrConv(bytName, vbUnicode), ""
           End If
          End If
         End If
        'Get the next chunk.
        lngBeginOfChunk = lngEndOfValue
        If InStrB(lngBeginOfChunk, bytThisChunk, bytBeginOfName, vbBinaryCompare) = 0 Then
          blnEndOfData = True
        End If
      Uploaded = True
      Exit Sub
      If Err.Number = VB_ERR_PATH_NOT_FOUND Then
        Err.Raise ERR_INVALID_TARGET, App.Title, "The Target specified does not exist."
        Err.Raise Err.Number, Err.Source, Err.Description
      End If
    End Sub
    Public Property Get Form() As Collection
        Set Form = m_formCol
    End Property
    Public Property Get FileName() As String
      FileName = m_strFileName
    End Property
    Public Property Let FileName(ByVal strNewValue As String)
      If Uploaded Then
        Err.Raise ERR_UPLOAD_CALLED, App.Title, "The Upload method has already been called."
        m_strFileName = strNewValue
      End If
    End Property
    Public Property Get OverWrite() As Boolean
      OverWrite = m_blnOverWrite
    End Property
    Public Property Let OverWrite(ByVal blnNewValue As Boolean)
      If Uploaded Then
        Err.Raise ERR_UPLOAD_CALLED, App.Title, "The Upload method has already been called."
        m_blnOverWrite = blnNewValue
      End If
    End Property
    Private Property Get Uploaded() As Boolean
      Uploaded = m_blnUploaded
    End Property
    Private Property Let Uploaded(ByVal blnNewValue As Boolean)
      m_blnUploaded = blnNewValue
    End Property
    Public Property Get Target() As String
      Target = m_strTarget
    End Property
    Public Property Let Target(ByVal NewValue As String)
      If Uploaded Then
        Err.Raise ERR_UPLOAD_CALLED, App.Title, "The Upload method has already been called."
        m_strTarget = NewValue
      End If
    End Property
    Private Function FileExists(ByVal FileName As String) As Boolean
      On Error GoTo FileExistsErr
      FileLen FileName
      FileExists = True
      Exit Function
      If Err.Number = VB_ERR_PATH_NOT_FOUND Then
        FileExists = False
      End If
    End Function
    Public Property Get TotalBytes() As Long
      TotalBytes = m_lngTotalBytes
    End Property
    Private Property Let TotalBytes(ByVal NewValue As Long)
      m_lngTotalBytes = NewValue
    End Property
  9. Compile the project

ASP Code

  1. Paste the following code to an editor such as Notepad or Microsoft Visual Interdev, and then save it as PostFile.asp:
    <%@ Language=VBScript %>
    <form enctype="multipart/form-data" action="uploadfile.asp" method="post" name="main1">
    <input name="file" type="file" size="50">
    <INPUT type="text" id=text1 name=text1><INPUT type="text" id=text2 name=text2>
    <input name="submit" type="submit" value="Upload">
  2. Copy the following code to an editor such as Notepad or Visual Interdev, and then save it as UploadFile.asp:
    <%@ Language=VBScript %>
      '//  ASPFileUpload.File API
      '//  Properties
      '//     FileName
      '//       - Read/Write 
      '//       - The file will be saved with this file name. 
      '//       - This property can only be set before calling Upload.
      '//       - If no value is specified, the original file name
      '//       - in the HTTP post will be used.
      '//     OverWrite
      '//       - Read/Write
      '//       - This property can only be set before calling Upload.
      '//       - If set to false and if the destination file exists, an error
      '//       - is raised. The default value is False.
      '//     Target 
      '//       - Read/Write
      '//       - The file will be written to this folder.
      '//       - This property can only be set before calling Upload.
      '//       - There is no default value for this property and it is required.
      '//      Form
      '//        - ReadOnly
      '//        - Scripting.Dictionary object
      '//        - Can access a specific item by using aspfileupload.Form("item").
      '//        - Acts like the asp form collection.
      '//        - Can enumerate all values in a collection with for each.
      '//        - Only filled after the Upload method is called.
      '//  Methods
      '//     Upload
      '//       - This method parses the HTTP Post and writes the file.
      '//  Other
      '//    - ASPFileUpload requires COM+
      '//    - Any call to the Request.Form() collection will cause the Upload
      '//      method to fail as the method references the Binary contents of the
      '//      Request object through the Request.BinaryRead method. 
      '//    - Also, if you access a variable in the Request collection without 
      '//      specifying the subcollection that it belongs to, the Request.Form collection 
      '//      may be searched. This causes an error in the Upload method.
      Dim strMsg 'As String
     ' On Error Resume Next
      dim fuFile
      set fuFile = server.CreateObject("aspFileupload.file")  
      'Set the destination folder.
      fuFile.Target = "C:\TEMP\AspFileUpload\"
      If Err.number = 0 Then
        strMsg = fuFile.FileName  & " was uploaded successfully."
        strMsg = "An error occurred when uploading your file: " & Err.Description 
      End If
      for each o in fuFile.Form
    	Response.Write o  & "<BR>"
    	Response.Write fuFile.Form.item("text1") & "  :  " & fuFile.Form.item("text2")
    '  Response.Write Request.Form("test")
     set fufile = nothing

Set Up the Server

  1. Create a folder on the Web server that will receive the uploaded files, such as C:\TEMP\AspFileUpload.
  2. Copy the ASPFileUpload.dll file to the Web server, and then register it by using the following command at the command prompt:
    regsvr32 PathToDLL\ASPFileUpload.dll
  3. Apply file permissions (Write access) for the users who you want to be able to upload the files.
  4. Click Start, point to Settings, and then click Control Panel.
  5. In Control Panel, click Administrative Tools, and then click Component Services to open Component Services in the Microsoft Management Console (MMC).
  6. Expand the Component Services node, the Computers node, the My Computer node, and the COM+ Applications node.
  7. Right-click the node, point to New, and then click Application.
  8. In the Install or Create a New Application dialog box, click Create an empty application, name the application, make sure that you click to select Server application, and then click Next.
  9. In the Set Application Identity dialog box, click This User, and then type the credentials for the appropriate user account. The user account must have Write access to the folder that will receive the uploaded file.
  10. Click Finish.
  11. Expand the node that you have just created for this application.
  12. Right-click the nod, point to New, and then click Component.
  13. Click Install new components, and locate the folder where you have saved and registered the .dll file, click the file, click Next, and then click Finish.
  14. Copy the Postfile.asp file and the Uploadfile.asp file to your Web root folder. By default, the Web root folder is C:\Inetpub\Wwwroot.
  15. Edit the target folder of Uploadfile.asp to reflect the folder that you created in step 1. The target folder assignment is located in the following line of code:
    fuFile.Target = "C:\TEMP\AspFileUpload\"

Upload a File

  1. In a Web browser, open the Postfile.asp page at the following URL:
  2. Select a file that you want to upload, and then click Upload.
  3. Check your upload folder. The file that you uploaded appears in this folder.


  • If you do not type a file name, and if you try to submit the Postfile.asp page, you receive a generic, server-side error message. You may want to modify the code to provide a more friendly error message on either the client side or on the server side.
  • If you require high volume upload capacity, Microsoft recommends that you buy or build a compiled, multithreaded component that can more efficiently handle the load than this Visual Basic component.
  • A potential security risk exists whenever you allow users to upload files to your Web server. This is especially true if your server is on the Internet, and if you allow anonymous uploads. You must correctly configure Windows permissions and IIS user authentication to make sure that you give users only the access that they require. This is important so that you do not allow users a way to gain access by bypassing the security controls of your system.


Article ID: 299692 - Last Review: January 4, 2012 - Revision: 7.0
  • Microsoft Active Server Pages 4.0
  • Microsoft Internet Information Services 5.0
kbaspobj kbcodesnippet kbconfig kbdeployment kbfile kbfso kbGuidelines kbhowto kbsample kbscript kbsecurity kbserver kbsetup kbwebserver KB299692

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