How to upload files to a Web server by using ASP

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.