How to upload files to a Web server by using ASP

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

Summary

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 http://msdn.microsoft.com/en-us/vstudio/ms788708.

Requirements

  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
    Else
    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)
    Else
    '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)
    Wend

    'Set the property.
    Me.FileName = StrConv(bytFileName, vbUnicode)

    'Convert the byte to Unicode.
    strFileName = Me.Target & Me.FileName

    Else
    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
    Else
    Err.Raise ERR_INVALID_FILENAME, App.Title, "The specified file name appears to be invalid."
    End If
    Else
    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
    Loop

    Close #lngFileNum

    TotalBytes = FileLen(strFileName)

    ' Exit Do
    Else
    If UCase(StrConv(bytName, vbUnicode)) = "SAVEAS" Then
    Me.FileName = StrConv(bytValue, vbUnicode)
    Else
    '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)
    Else
    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
    Loop

    Uploaded = True

    Exit Sub

    UploadErr:

    If Err.Number = VB_ERR_PATH_NOT_FOUND Then
    Err.Raise ERR_INVALID_TARGET, App.Title, "The Target specified does not exist."
    Else
    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."
    Else
    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."
    Else
    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."
    Else
    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

    FileExistsErr:
    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 %>
    <html>
    <head>
    </head>
    <body>
    <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">
    </form>
    </body>
    </html>
  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\"
    fuFile.Upload

    If Err.number = 0 Then
    strMsg = fuFile.FileName & " was uploaded successfully."
    Else
    strMsg = "An error occurred when uploading your file: " & Err.Description
    End If
    for each o in fuFile.Form
    Response.Write o & "<BR>"

    next

    Response.Write fuFile.Form.item("text1") & " : " & fuFile.Form.item("text2")
    ' Response.Write Request.Form("test")
    set fufile = nothing
    %>
    <html>
    <head></head>
    <body>
    <%=strMsg%>
    </body>
    </html>

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:
    http://YourWebServer/Postfile.asp
  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.

Troubleshooting

  • 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.
Properties

Article ID: 299692 - Last Review: Jan 4, 2012 - Revision: 1

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