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Published: Wednesday, May 28, 2003

Displaying the Files in a Directory using a DataGrid

By Scott Mitchell


An Updated Version of This Article...
This article was written in 2003 and shows how to display files in the DataGrid Web control. Since ASP.NET 2.0, the DataGrid has been deprecated in favor of the GridView control. A new article, Displaying Files and Folders in a GridView, examines how to display files and folders in a GridView control.

Introduction


There are many scenarios Web developers face where they need to be able to display information about the Web server's file system. For example, a Web hosting company might want to provide a "Control Panel" that allows their clients to edit their Web site's files using a Web interface. A developer working on her company's intranet might want to create a Web page that provides a nice listing of business reports that reside in an intranet-accessible directory.

- continued -

In classic ASP, to access the Web server's file system developers used the FileSystemObject library. (For more on the FileSystemObject library check out the FileSystemObject FAQ Category at ASPFAQs.com.) In .NET, there is a set of classes in the System.IO namespace that allow for programmatic access to the file system.

Accessing file system information in ASP.NET is about as easy (if not easier) as it was in classic ASP. The real benefit with ASP.NET comes in displaying the file system information. As we will see in this article, the file system information can be bound to any of the data Web controls, such as the DataGrid, DataList, or Repeater. This means that the information can be displaying in an aesthetically-pleasing manner with minimal time.

Examining Accessing the File System Using ASP.NET


The .NET Framework contains two classes for accessing directory information, and two classes for accessing file information. To access directory information, use either the Directory or the DirectoryInfo class; to access file information, use either the File class or the FileInfo class.

The differences between the two classes is the level of information it returns and how it is used. The Directory and File classes are static classes, meaning that you don't have to create an instance of the class in order to use its methods. These classes are useful if you want to quickly perform some directory-related function. For example, to delete a file, you can use File.Delete(filePath); to determine if a directory exists, you can use Directory.Exists(directoryPath).

The Info classes - FileInfo and DirectoryInfo - require that you first create an instance of the class and specify the file or directory's name in the constructor. For example, to delete a file using the FileInfo class, you'd use the following code:

Dim myFile as FileInfo = New FileInfo(filePath)
myFile.Delete()

Getting a List of Files in a Directory


Both the Directory and DirectoryInfo classes contain a method to get all of the files in a directory (or to get all of the files in a directory matching some wildcard expression, like *.htm) - this method is called GetFiles() and is used as follows:

' --- Directory Example ----
Dim files() as String = Directory.GetFiles(directoryPath[, optionalWildCard])

' --- DirectoryInfo Example ----
Dim myDir as DirectoryInfo = New DirectoryInfo(directoryPath)
Dim fileInfos() as FileInfo = myDir.GetFiles([optionalWildCard])

As you can see, the Directory.GetFiles() method accepts one or two parameters. You must specify the path of the directory whose files you want to get, and you may optionally specify a wildcard path (like *.aspx). This method returns a String array, which contains the filenames in the directory (that match the wildcard expression, if supplied). The DirectoryInfo.GetFiles() method doesn't accept a directory path input since the directory's path is already known. Unlike the Directory.GetFiles() method, the DirectoryInfo.GetFiles() method returns an array of FileInfo objects, not Strings.

Displaying a Directory's Files in a DataGrid


To display a directory's files in a DataGrid (or DataList or Repeater) all we need to do is assign the String array or FileInfo array to the DataGrid's DataSource property and then call the DataGrid's DataBind() method. For this example, we'll use the DirectoryInfo.GetFiles() method instead of the Directory.GetFiles() method. If we opted to use the Directory.GetFiles() method then all we'd be able to show in the DataGrid is the file's name. By using the DirectoryInfo.GetFiles() method instead, we can display other attributes of the file, such as its size, last modified date, and so on.

<%@ Import Namespace="System.IO" %>
<script language="VB" runat="server">
  Sub Page_Load(sender as Object, e as EventArgs)
    Dim dirInfo as New DirectoryInfo(Server.MapPath(""))
    
    articleList.DataSource = dirInfo.GetFiles("*.aspx")
    articleList.DataBind()
  End Sub
</script>

<asp:DataGrid runat="server" id="articleList" Font-Name="Verdana"
    AutoGenerateColumns="False" AlternatingItemStyle-BackColor="#eeeeee"
    HeaderStyle-BackColor="Navy" HeaderStyle-ForeColor="White"
    HeaderStyle-Font-Size="15pt" HeaderStyle-Font-Bold="True">
  <Columns>
    <asp:HyperLinkColumn DataNavigateUrlField="Name" DataTextField="Name" 
           HeaderText="File Name" />
    <asp:BoundColumn DataField="LastWriteTime" HeaderText="Last Write Time"
        ItemStyle-HorizontalAlign="Center" DataFormatString="{0:d}" />
    <asp:BoundColumn DataField="Length" HeaderText="File Size"
		ItemStyle-HorizontalAlign="Right" 
		DataFormatString="{0:#,### bytes}" />
  </Columns>
</asp:DataGrid>  
  
[View a Live Demo!]

As the above code sample shows, all that it takes to bind the list of files in a directory to an ASP.NET DataGrid is simply setting the DataGrid's DataSource to the result of the GetFiles() method. Specifically, in the above code sample the list of files with the extension .aspx that reside in the same directory that the ASP.NET Web page itself resides in are displayed.

Particular attributes of the FileInfo class can be displayed in the various DataGrid columns by simply setting the column's properties accordingly. For example, the FileInfo.Length property is displayed in the last BoundColumn by setting the BoundColumn's DataField property to Length. (For a full list of FileInfo properties, see the technical documentation.)

Now that we've seen how to simply display the list of files in a directory, let's look at making the example a bit more useful by allowing users to delete a file with the click of a button. We'll see how to accomplish this in Part 2.

  • Read Part 2!



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