You want a user to be able to upload a file to the web server for immediate processing, without having to first store the file.
Implement the solution described in Recipe 15.2 but instead of writing the file to the filesystem, use the input stream containing the uploaded file to process the data.
For the .aspx file, follow the steps for
implementing the .aspx file in Recipe 15.2 and then, if you like, add a control
that will show the results of the processing—for example, a
DataGrid control to display the contents of an
uploaded XML file.
In the code-behind file for the page, use the .NET language of your choice to:
Verify, in the Upload button click event handler, that the file has been uploaded—that is, that the length of the filename and the file contents are both greater than 0—and (if appropriate) that it is a valid XML file.
Load the updated data and, if you elected to include a control for showing the contents of the uploaded file, bind the uploaded data to the control—for example, a
DataGridcontrol.
Example 15-8 through Example 15-10 show the .aspx file and
VB and C# code-behind files for an application we’ve
written to illustrate this solution. The initial output is identical
to Recipe 15.2s
example output and is shown in Figure 15-3.
This recipe demonstrates the concept of uploading files and processing them without having to store them to the local filesystem, as you might do with the contents of an XML file for example. This eliminates the problems of files being uploaded with the same names, inadvertently filling the hard drive, and the security aspects of allowing the ASPNET write privileges on the local filesystem.
The example that we’ve written to illustrate this
solution is similar to that described in Recipe 15.2, except that instead of saving the file
contents to the filesystem, we process it immediately by loading the
uploaded data into a DataSet and then binding the
DataSet to a DataGrid.
What’s more, our example uses the basic
.aspx file described in Recipe 15.2 with a few changes to support using the
page for uploading an XML file and displaying its contents.
In the Page_Load method of the code-behind, the
table containing the upload controls is made visible and the
DataGrid invisible. (We’ll switch
the visibility of the two at a later stage to display the contents of
the processed file.)
When the user clicks the Upload button, the
btnUpload_ServerClick method is executed. The code
for making sure a file was uploaded is identical to our example code
in Recipe 15.2. An additional check
has been added in this example to ensure the uploaded file is an XML
file because this example is expecting XML data. Because the same
page is used to display the contents of the uploaded file, the table
containing the upload controls now needs to be made invisible and the
DataGrid used to display the contents of the
uploaded file made visible.
Next, we use PostedFile.InputStream to load the
data into the DataSet. In our example, the XML
file shown in Example 15-7 is being uploaded and
because of its formatting can be read directly into the
DataSet. With other types of data, you may need to
do other processing. In addition, production code should validate the
content type of the posted file as well as the contents of the file
itself to ensure the uploaded file is valid.
Example 15-7. XML file uploaded
<Root>
<Book>
<BookID>1</BookID>
<Title>Access Cookbook</Title>
<ISBN>0-596-00084-7</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>2</BookID>
<Title>Perl Cookbook</Title>
<ISBN>1-565-92243-3</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>3</BookID>
<Title>Java Cookbook</Title>
<ISBN>0-596-00170-3</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>4</BookID>
<Title>JavaScript Application Cookbook</Title>
<ISBN>1-565-92577-7</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>5</BookID>
<Title>VB .Net Language in a Nutshell</Title>
<ISBN>0-596-00092-8</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>6</BookID>
<Title>Programming Visual Basic .Net</Title>
<ISBN>0-596-00093-6</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>7</BookID>
<Title>Programming C#</Title>
<ISBN>0-596-00117-7</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>8</BookID>
<Title>.Net Framework Essentials</Title>
<ISBN>0-596-00165-7</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
<Book>
<BookID>9</BookID>
<Title>COM and .Net Component Services</Title>
<ISBN>0-596-00103-7</ISBN>
<Publisher>O'Reilly</Publisher>
</Book>
</Root>The last step in our example is to bind the
DataGrid on the form to the
DataSet containing the uploaded XML file. Figure 15-4 shows the output for the uploaded and
processed file. For more information on data binding, refer to the
recipes in Chapter 1.
Chapter 2 for validation controls;
HtmlInputFile class documentation in the MSDN
library for more information on file uploads
Example 15-8. Upload file and process (.aspx)
<%@ Page Language="vb" AutoEventWireup="false"
Codebehind="CH15FileUploadAndProcessVB.aspx.vb"
Inherits="ASPNetCookbook.VBExamples.CH15FileUploadAndProcessVB" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>File Upload And Process</title>
<link rel="stylesheet" href="css/ASPNetCookbook.css">
</head>
<body leftmargin="0" marginheight="0" marginwidth="0" topmargin="0">
<form id="frmUpload" method="post" runat="server"
enctype="multipart/form-data">
<table width="100%" cellpadding="0" cellspacing="0" border="0">
<tr>
<td align="center">
<img src="images/ASPNETCookbookHeading_blue.gif">
</td>
</tr>
<tr>
<td class="dividerLine">
<img src="images/spacer.gif" height="6" border="0"></td>
</tr>
</table>
<table width="90%" align="center" border="0">
<tr>
<td align="center"> </td>
</tr>
<tr>
<td align="center" class="PageHeading">
File Upload And Process (VB)
</td>
</tr>
<tr>
<td><img src="images/spacer.gif" height="10" border="0"></td>
</tr>
<tr>
<td align="center">
<!-- The following table is displayed when the user is
uploading a file -->
<table id="tabUpload" runat="server" width="60%" border="0">
<tr>
<td align="center">
<input id="txtUpload" runat="server" type="file" >
</td>
</tr>
<tr>
<td align="center">
<br />
<input id="btnUpload" runat="server"
type="button" value="Upload" name="btnUpload">
</td>
</tr>
</table>
<!-- The following datagrid is displayed to show the data from
the uploaded file -->
<asp:DataGrid id="dgBooks" runat="server"
BorderColor="000080"
BorderWidth="2px"
AutoGenerateColumns="False"
width="100%">
<HeaderStyle HorizontalAlign="Center"
ForeColor="#FFFFFF"
BackColor="#000080"
Font-Bold=true
CssClass="TableHeader" />
<ItemStyle BackColor="#FFFFE0"
cssClass="TableCellNormal" />
<AlternatingItemStyle BackColor="#FFFFFF"
cssClass="TableCellAlternating" />
<Columns>
<asp:BoundColumn HeaderText="Title" DataField="Title" />
<asp:BoundColumn HeaderText="ISBN" DataField="ISBN"
ItemStyle-HorizontalAlign="Center" />
<asp:BoundColumn HeaderText="Publisher" DataField="Publisher"
ItemStyle-HorizontalAlign="Center" />
</Columns>
</asp:DataGrid>
</td>
</tr>
</table>
</form>
</body>
</html>Example 15-9. Upload file and process code-behind (.vb)
Option Explicit On
Option Strict On
'-----------------------------------------------------------------------------
'
' Module Name: CH15FileUploadAndProcessVB.aspx.vb
'
' Description: This module provides the code behind for the
' CH15FileUploadAndProcessVB.aspx page
'
'*****************************************************************************
Imports Microsoft.VisualBasic
Imports System
Imports System.Data
Imports System.IO
Imports System.Web.UI
Namespace ASPNetCookbook.VBExamples
Public Class CH15FileUploadAndProcessVB
Inherits System.Web.UI.Page
'controls on the form
Protected tabUpload As System.Web.UI.HtmlControls.HtmlTable
Protected txtUpload As System.Web.UI.HtmlControls.HtmlInputFile
Protected WithEvents btnUpload As HtmlControls.HtmlInputButton
Protected dgBooks As System.Web.UI.WebControls.DataGrid
'*************************************************************************
'
' ROUTINE: Page_Load
'
' DESCRIPTION: This routine provides the event handler for the page load
' event. It is responsible for initializing the controls
' on the page.
'-------------------------------------------------------------------------
Private Sub Page_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
If (Not Page.IsPostBack) Then
'make the table containing the upload controls visible and
'the datagrid with the uploaded data invisible
tabUpload.Visible = True
dgBooks.Visible = False
End If
End Sub 'Page_Load
'***************************************************************************
'
' ROUTINE: btnUpload_ServerClick
'
' DESCRIPTION: This routine provides the event handler for the upload
' button click event. It is responsible processing the
' file and displaying the contents.
'---------------------------------------------------------------------------
Private Sub btnUpload_ServerClick(ByVal sender As Object, _
ByVal e As System.EventArgs) _
Handles btnUpload.ServerClick
Dim ds As DataSet
Dim filename As String
'make sure file was specified, was found, and is an xml file
filename = txtUpload.PostedFile.FileName.Trim
If ((filename.Length > 0) And _
(txtUpload.PostedFile.ContentLength > 0) And _
(txtUpload.PostedFile.ContentType.Equals("text/xml"))) Then
'make the table containing the upload controls invisible and
'the datagrid with the uploaded data visible
tabUpload.Visible = False
dgBooks.Visible = True
'load uploaded data into the dataset
ds = New DataSet
ds.ReadXml(txtUpload.PostedFile.InputStream)
'bind the data to the datagrid on the form
dgBooks.DataSource = ds
dgBooks.DataBind( )
Else
'production code should notify user of upload error here
End If
End Sub 'btnUpload_ServerClick
End Class 'CH15FileUploadAndProcessVB
End NamespaceExample 15-10. Upload file and process code-behind (.cs)
//----------------------------------------------------------------------------
//
// Module Name: CH15FileUploadAndProcessCS.aspx.cs
//
// Description: This module provides the code behind for the
// CH15FileUploadAndProcessCS.aspx page
//
//****************************************************************************
using System;
using System.Data;
using System.IO;
namespace ASPNetCookbook.CSExamples
{
public class CH15FileUploadAndProcessCS : System.Web.UI.Page
{
// controls on the form
protected System.Web.UI.HtmlControls.HtmlTable tabUpload;
protected System.Web.UI.HtmlControls.HtmlInputFile txtUpload;
protected System.Web.UI.HtmlControls.HtmlInputButton btnUpload;
protected System.Web.UI.WebControls.DataGrid dgBooks;
//************************************************************************
//
// ROUTINE: Page_Load
//
// DESCRIPTION: This routine provides the event handler for the page
// load event. It is responsible for initializing the
// controls on the page.
//------------------------------------------------------------------------
private void Page_Load(object sender, System.EventArgs e)
{
// wire the upload button event handler
this.btnUpload.ServerClick +=
new EventHandler(this.btnUpload_ServerClick);
if (!Page.IsPostBack)
{
// make the table containing the upload controls visible and
// the datagrid with the uploaded data invisible
tabUpload.Visible = true;
dgBooks.Visible = false;
}
} // Page_Load
//************************************************************************
//
// ROUTINE: btnUpload_ServerClick
//
// DESCRIPTION: This routine provides the event handler for the upload
// button click event. It is responsible processing the
// file and displaying the contents.
//------------------------------------------------------------------------
private void btnUpload_ServerClick(object sender, System.EventArgs e)
{
string filename = null;
DataSet ds = null;
// make sure file was specified, was found, and is an xml file
filename = txtUpload.PostedFile.FileName.Trim( );
if ((filename.Length > 0) &&
(txtUpload.PostedFile.ContentLength > 0) &&
(txtUpload.PostedFile.ContentType.Equals("text/xml")))
{
// make the table containing the upload controls invisible and
// the datagrid with the uploaded data visible
tabUpload.Visible = false;
dgBooks.Visible = true;
//load uploaded data into the dataset
ds = new DataSet( );
ds.ReadXml(txtUpload.PostedFile.InputStream);
// bind the data to the datagrid on the form
dgBooks.DataSource = ds;
dgBooks.DataBind( );
}
else
{
// production code should notify user of upload error here
}
} // btnUpload_ServerClick
} // CH15FileUploadAndProcessCS
}