ASP.NET Cookbook

15.1. Downloading a File from the Web Server

Problem

You need to provide the ability for a user to download a file from the web server.

Solution

Use the Directory and FileInfo classes to gather and present the names of the files you want to make available for download to the user. Display their names in a listbox with a button to initiate the download. When the user clicks the button, stream the selected file to the browser.

In the .aspx file, add a listbox and a Download (or equivalently named) button.

In the code-behind class for the page, use the .NET language of your choice to:

1. Create a list of available files to download using the GetFiles method of the Directory class.

2. Populate the ListBox with the filenames by binding the list of files to the ListBox.

3. Process the Download button click event and stream the selected file to the browser using the Response object.

Example 15-1 through Example 15-3 show the .aspx file and VB and C# code-behind files for an application that illustrates our solution by populating the listbox with a list of files located in the application’s images directory. The populated listbox is shown in Figure 15-1, and the prompt that is output when the user selects a file and clicks Download is shown in Figure 15-2.

Figure 15-1. Listing files to be downloaded

Figure 15-2. File ...