In this article I am explaining how to upload multiple files by dynamically adding FileUpload controls using JavaScript.

Here I will explain how one can create a multiple file uploading controls in a very simple manner and very less amount of code. With this example one will able to perform the following functions

1. Add FileUpload Controls dynamically using JavaScript

2. Remove FileUpload Controls dynamically using JavaScript.

Since I am using JavaScript the UI becomes elegant since no need of postback or AJAX to add or remove FileUpload Controls.

Adding and Removing FileUpload Controls using JavaScript

Below is the HTML markup of the page. As you can see I have added a HTML button in order to add new FileUpload Controls, a DIV FileUploadContainer in which the dynamic FileUpload Controls will be added and a ASP.Net Upload Button in order to upload the files when the Upload Button us clicked.

An important think to note that you will need to add enctype="multipart/form-data to the form in order to allow the uploading of files through dynamic FileUpload controls.

<form id="form1" runat="server" enctype="multipart/form-data" method = "post">
    <span style ="font-family:Arial">Click to add files</span>&nbsp;&nbsp;
    <input id="Button1" type="button" value="add" onclick = "AddFileUpload()" />
    <br /><br />
    <div id = "FileUploadContainer">
        <!--FileUpload Controls will be added here -->
    </div>
    <br />
    <asp:Button ID="btnUpload" runat="server"
      Text="Upload" OnClick="btnUpload_Click" />
</form>

Now in order to add and remove the FileUpload Controls dynamically here is the JavaScript functions that are used.

<script type = "text/javascript">
var counter = 0;
function AddFileUpload()
{
     var div = document.createElement('DIV');
     div.innerHTML = '<input id="file' + counter + '" name = "file' + counter +
                     '" type="file" />' +
                     '<input id="Button' + counter + '" type="button" ' +
                     'value="Remove" onclick = "RemoveFileUpload(this)" />';
     document.getElementById("FileUploadContainer").appendChild(div);
     counter++;
}
function RemoveFileUpload(div)
{    
document.getElementById("FileUploadContainer").removeChild(div.parentNode);
}
</script>

As you will notice above first I am creating a DIV element and then adding a HTML FileUpload Control along with a HTML Button in order to remove the FileUpload Controls. Also onclick of the Remove button I am calling the RemoveFileUpload function which removes the dynamically created FileUpload control. 

Server Side Uploading of Files

Server Side I have written the following code in the Click event of the Upload Button

C#

protected void btnUpload_Click(object sender, EventArgs e)
{
    for (int i = 0; i < Request.Files.Count; i++)
    {
        HttpPostedFile PostedFile = Request.Files[i];
        if (PostedFile.ContentLength > 0)
        {
            string FileName = System.IO.Path.GetFileName(PostedFile.FileName);
            PostedFile.SaveAs(Server.MapPath("Files\\") + FileName);
        }
    }
}

VB.Net

Protected Sub btnUpload_Click(ByVal sender As Object, ByVal e As System.EventArgs)
  For i As Integer = 0 To Request.Files.Count – 1
   Dim PostedFile As HttpPostedFile = Request.Files(i)
   If PostedFile.ContentLength > 0 Then
      Dim FileName As String = System.IO.Path.GetFileName(PostedFile.FileName)
      PostedFile.SaveAs(Server.MapPath("Files\") + FileName)
   End If
  Next
End Sub 

In the above code snippet I am simply looping through the Request.Files Collection which contains the uploaded Files and then I am saving each of them one by one in a Folder called Files within my website root folder. 

Web.Config Configurations

Since this article deals with uploading multiple files it is important to discuss the maximum file size allowed. By default ASP.Net allows files of size maximum 4MB at a time. Hence in order to upload more data we will need to increase this limit. Refer the httpRuntime section of the Web.Config, if it is not present in your Web.Config you can simply paste the one given below in your file.

<httpRuntime
  executionTimeout="110"
  maxRequestLength="4096"
  requestLengthDiskThreshold="80"
  useFullyQualifiedRedirectUrl="false"
  minFreeThreads="8"
  minLocalRequestFreeThreads="4"
  appRequestQueueLimit="5000"
  enableKernelOutputCache="true"
  enableVersionHeader="true"
  requireRootedSaveAsPath="true"
  enable="true"
  shutdownTimeout="90"
  delayNotificationTimeout="5"
  waitChangeNotification="0"
  maxWaitChangeNotification="0"
  enableHeaderChecking="true"
  sendCacheControlHeader="true"
  apartmentThreading="false"
/>

In order to increase the maximum file size limit you will need to change the value of the maxRequestLength attribute in kilobytes (KB). For example if you want to set the upload limit to 10 MB you will have to set the value to 10240. Another important parameter is executionTimeout. It determines the maximum amount of time in seconds ASP.Net will process the request and after which it will stop the processing. By default the value is 110 seconds. You can modify it to the value that suits your needs



The above code has been tested in the following browsers

A typical web.config file in v2.0 could have the following section which is placed directly under the root <configuration> section.

<connectionStrings>
    <remove name="LocalSqlServer" />
    <add name="LocalSqlServer" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient"/>
    <add name="MainConnStr" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|main.mdf;User Instance=true" providerName="System.Data.SqlClient"/>
</connectionStrings>

connectionStrings>
    <remove name="LocalSqlServer" />
    <add name="LocalSqlServer" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient"/>
    <add name="MainConnStr" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|main.mdf;User Instance=true" providerName="System.Data.SqlClient"/>
</connectionStrings>

You can reference this directly from code using:

[C#]
string connStr = ConfigurationManager.ConnectionStrings["MainConnStr"].ConnectionString;

[VB]
Dim connStr As String = ConfigurationManager.ConnectionStrings("MainConnStr").ConnectionString

Note that the namespace for this is System.Configuration so for a console application the full namespace is required.

Or you can reference this declaratively within the ConnectionString property of a SqlDataSource:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
  ConnectionString="<%$ ConnectionStrings:MainConnStr %>"
  SelectCommand="SELECT [au_id], [au_lname], [au_fname], [state] FROM [authors]" />

Introduction

When Microsoft released its flavour of AJAX framework named "ASP.NET AJAX" as part of ASP.NET 3.0 preview, it did not have much competency when compared to other AJAX frameworks. But when I evaluated ASP.NET AJAX 4.0, I was really inspired with the new features that are completely focused on your browser technologies such as XHTML and JavaScript. I really admired the effort made by the ASP.NET AJAX team. There could not be any second opinion when you see the following features:

- Template based client side programming
- DataView and DataContext
- Live Data Binding

Template Programming

Template provides pattern to design a web UI form and enables to put placeholders for runtime data. For example, I've designed a web page to display AdventureWorks database Product data through ADO.NET data service. The entity model (edmx) is:



The service code is:

public class AWProductDataService : DataService
{  
    public static void InitializeService(IDataServiceConfiguration config)
    {
        config.SetEntitySetAccessRule("*", EntitySetRights.All);
    }
}

By ASP.NET templates, the page looks like:

<%@ Page Language="C#" AutoEventWireup="true"
  CodeBehind="ClientTemplateAndDataViewDemo.aspx.cs"
  Inherits="CoreEnhancements.AJAX.ClientTemplateAndDataViewDemo" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Microsoft Tech.Ed - Client-side Templating Demo</title>
    <style type="text/css">
        .sys-template {display:none}
    </style>    
    <script type="text/javascript" src="../scripts/MicrosoftAjax.debug.js"></script>
    <script type="text/javascript" src="../scripts/MicrosoftAjaxTemplates.debug.js">
    </script>
    <script type="text/javascript" src="../scripts/MicrosoftAjaxAdoNet.debug.js">
    </script>
    <script type="text/javascript">
        var dataContext = new Sys.Data.AdoNetDataContext();
        dataContext.set_serviceUri("AWProductDataService.svc");
        dataContext.initialize();
    </script>
</head>
<body xmlns:sys="javascript:Sys" xmlns:dataview="javascript:Sys.UI.DataView"
  sys:activate="*">
    <form id="form1" runat="server">   
    <div> 
    <table border="1">
        <thead>
            <tr>
                <td>Name</td>
                <td>List Price</td>
                <td>Size</td>
                <td>Weight</td>
            </tr>
        </thead>   
    <tbody class="sys-template" sys:attach="dataview" dataview:autofetch="true"
    dataview:dataprovider="{{ dataContext }}"
    dataview:fetchoperation="Products">                
        <tr>
          <td>{binding Name }</td>
          <td>{binding ListPrice}</td>
          <td>{binding Size}</td>
          <td>{binding Weight}</td>
        </tr>
    </tbody>
    </table>
    </div> 
    </form>
</body>

I have used a typical HTML table for displaying the data. You can see some new attributes in <TBODY> and data place holders in <TD>. ASP.NET AJAX 4.0 has a dedicated template engine to parse these new attributes and data place holders. ASP.NET AJAX has defined a rich set of attributes and data placeholder patterns collectively called as expression language which are none other than X(HT)ML and JavaScript. Remarkable point here is its XHTML compliance, so these are not custom attributes in the regular HTML elements. The class attribute of the <TBODY> is set to sys-template, which is a convention used to hide the initial template from the user. .sys-template {display:none} The fields or properties of a data item which are needed to be rendered on data place holders can be expressed by {{ }} or { }.

DataContext

Template requires data for its place holders as contexts. The data context enables to bind any JavaScript array or objects to template. The real power of data context is to interact with JSON/ATOM based web services. ASP.NET AJAX provides two data contexts in MicrosoftAjaxAdoNet.js:

- Sys.Data.DataContext
- Sys.Data.AdoNetDataContext

The data context tracks all changes to the data automatically using new Sys.Observer object. AdoNetDataContext supports additional features for ADO.NET data services such as identity management, links and association between entity sets. The below code sample describes how to interact with AdventureWorks Product's ADO.NET data service:

var dataContext = new Sys.Data.AdoNetDataContext();
dataContext.set_serviceUri("AWProductDataService.svc");
dataContext.initialize();

The set_serviceUri() method is used to interact with WCF AJAX or ADO.NET data service. The initialize() method does initialization or invocation.

Data View

This is the fundamental component for templates to display data defined in System.UI.DataView. This is similar to server side data source component supports to bind any JavaScript object or array or to any ASP.NET AJAX component. It has two properties to bind a data set:

- data - To bind a JavaScript array or object
- dataprovider - To bind to a WCF service

The fetchoperation property is used to set which method needs to be invoked for fetching data. In the code snippet 1, I've set the dataContext declared in code snippet 2 as data source. To run this application, refer to the following ASP.NET AJAX client side libraries:

- MicrosoftAjax.js
- MicrosoftAjaxTemplates
- MicrosoftAjaxAdoNet

The xmlns:sys declares the namespace Sys for the entire page (Code 1. Line 2). The xmlns:dataview declares DataView control. A data view instance has been associated with <TBODY> using sys:attach.

The following figure shows the conceptual model of the template programming:



The output code is: