Professional ASP.NET 3.5 in C# and Visual Basic Part 119 docx

Evjen c25.tex V2 - 01/28/2008 3:42pm Page 1140
Chapter 25: File I/O and Streams
Working with Drives, Directories, and Files
Many times in your ASP.NET applications, you need to interact with the local file system, reading
directory structures, reading and writing to files, or performing many other tasks. The
System.IO
namespace within the .NET Framework makes working with file system directories and files very easy.
While working with the classes in the
System.IO
namespace, keep in mind that because your ASP.NET
applications are executing on the server, the file system you are accessing is the one your Web application
is running on. You, of course, cannot use an ASP.NET application to access the end user’s file system.
The DriveInfo Class
You can start working with the
System.IO
namespace at the top of the directory tree by using a great
new addition to the .NET 3.5 class libraries, the
DriveInfo
class. This class supplements the
GetLog-
icalDrives()
method of the
Directory
class included in prior versions of the .NET Framework. It
provides you with extended information on any drive registered with the server’s local file system. You
can get information such as the name, type, size, and status of each drive. Listing 25-1 shows you how to
create a
DriveInfo
object and display local drive information on a Web page.
Listing 25-1: Displaying local drive information
VB

<
script runat="server"
>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Dim drive As New System.IO.DriveInfo("C:
\
")
lblDriveName.Text = drive.Name
lblDriveType.Text = drive.DriveType.ToString()
lblAvailableFreeSpace.Text = drive.AvailableFreeSpace.ToString()
lblDriveFormat.Text = drive.DriveFormat
lblTotalFreeSpace.Text = drive.TotalFreeSpace.ToString()
lblTotalSize.Text = drive.TotalSize.ToString()
lblVolumeLabel.Text = drive.VolumeLabel
End Sub
<
/script
>
<
html xmlns=" />>
<
head runat="server"
>
<
title
>
Displaying Drive Information
<
/title
>

<
/head
>
<
body
>
<
form id="form1" runat="server"
>
<
div
>
<
table
>
<
tr
><
td
>
Drive Name:
<
/td
><
td
>
<
asp:Label ID="lblDriveName" runat="server" Text="Label" /
>
<

/td
><
/tr
>
<
tr
><
td
>
Drive Type:
<
/td
><
td
>
<
asp:Label ID="lblDriveType" runat="server" Text="Label"/
>
<
/td
><
/tr
>
<
tr
><
td
>
Available Free Space:
<

/td
><
td
>
<
asp:Label ID="lblAvailableFreeSpace" runat="server" Text="Label" /
>
<
/td
><
/tr
>
<
tr
><
td
>
Drive Format:
<
/td
><
td
>
<
asp:Label ID="lblDriveFormat" runat="server" Text="Label" /
>
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Chapter 25: File I/O and Streams
<

/td
><
/tr
>
<
tr
><
td
>
Total Free Space:
<
/td
><
td
>
<
asp:Label ID="lblTotalFreeSpace" runat="server" Text="Label" /
>
<
/td
><
/tr
>
<
tr
><
td
>
Total Size:
<

/td
><
td
>
<
asp:Label ID="lblTotalSize" runat="server" Text="Label" /
>
<
/td
><
/tr
>
<
tr
><
td
>
Volume Label
<
/td
><
td
>
<
asp:Label ID="lblVolumeLabel" runat="server" Text="Label" /
>
<
/td
><
/tr

>
<
/table
>
<
/div
>
<
/form
>
<
/body
>
<
/html
>
C#
<
script runat="server"
>
protected void Page_Load(object sender, EventArgs e)
{
System.IO.DriveInfo drive = new System.IO.DriveInfo(@"C:
\
");
lblDriveName.Text = drive.Name;
lblDriveType.Text = drive.DriveType.ToString();
lblAvailableFreeSpace.Text = drive.AvailableFreeSpace.ToString();
lblDriveFormat.Text = drive.DriveFormat;
lblTotalFreeSpace.Text = drive.TotalFreeSpace.ToString();

lblTotalSize.Text = drive.TotalSize.ToString();
lblVolumeLabel.Text = drive.VolumeLabel;
}
<
/script
>
One of the more interesting properties in the sample is the
DriveType
enumeration. This read-only enu-
meration tells you what the drive type is, for example CD-ROM, Fixed, Ram, or Removable. Figure 25-1
shows you what the page looks like when you view it in a browser.
Figure 25-1
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Chapter 25: File I/O and Streams
You can also enumerate through all the drives on the local file system by using the
DriveInfo
’s static
GetDrives()
method. Listing 25-2 shows an example of enumerating through the local file system drives
and adding each drive as a root node to a TreeView control.
Listing 25-2: Enumerating through local file system drives
VB
<
script runat="server"
>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
If (Not Page.IsPostBack) Then
For Each drive As System.IO.DriveInfo In System.IO.DriveInfo.GetDrives()
Dim node As TreeNode = New TreeNode()

node.Value = drive.Name
’ Make sure the drive is ready before we access it
If (drive.IsReady) Then
node.Text = drive.Name & _
" - (free space: " & drive.AvailableFreeSpace & ")"
Else
node.Text = drive.Name & " - (not ready)"
End If
Me.TreeView1.Nodes.Add(node)
Next
End If
End Sub
<
/script
>
<
html xmlns=" />>
<
head runat="server"
>
<
title
>
Enumerate Local System Drives
<
/title
>
<
/head
>

<
body
>
<
form id="form1" runat="server"
>
<
div
>
<
table
>
<
tr
>
<
td style="width: 100px" valign="top"
>
<
asp:TreeView ID="TreeView1" runat="server"
><
/asp:TreeView
>
<
/td
>
<
/tr
>
<

/table
>
<
/div
>
<
/form
>
<
/body
>
<
/html
>
C#
<
script runat="server"
>
protected void Page_Load(object sender, EventArgs e)
{
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Chapter 25: File I/O and Streams
if (!Page.IsPostBack)
{
foreach (System.IO.DriveInfo drive in System.IO.DriveInfo.GetDrives())
{
TreeNode node = new TreeNode();
node.Value = drive.Name;
//Make sure the drive is ready before we access it

if (drive.IsReady)
node.Text = drive.Name +
" - (free space: " + drive.AvailableFreeSpace + ")";
else
node.Text = drive.Name + " - (not ready)";
this.TreeView1.Nodes.Add(node);
}
}
}
<
/script
>
Notice that, in this sample, the drive object’s
IsReady
property is a read-only property used to test
whether the drive is accessible. If you are enumerating drives, it’s always a good idea to test for this
before attempting to access any of the other drive properties because removable drives and network
drives may not always be available when your code is executed. Figure 25-2 shows what the page looks
like when viewed in the browser.
Figure 25-2
The Directory and DirectoryInfo Classes
Next, you can build on the previous examples and add the capability to browse through the
system’s directory structure. The
System.IO
namespace contains two classes for working with file system
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Chapter 25: File I/O and Streams
directories, the
Directory

and
DirectoryInfo
classes. The
Directory
class exposes static methods you
can use to create, move, and delete directories. The
DirectoryInfo
represents a specific directory and
lets you perform many of the same actions as the
Directory
class on the specific directory. Additionally,
it enumerates child directories and files.
To continue the example, you can use the
GetDirectories()
method of the
DirectoryInfo
class to
create a recursive method that loops through each system drive directory tree and adds the directories
to a TreeView control to create a small directory browser. Listing 25-3 shows how to create a recursive
LoadDirectories()
method to walk through the local file system’s directory structure.
Listing 25-3: Enumerating file system directories
VB
<
script runat="server"
>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
If (Not Page.IsPostBack) Then
For Each drive As System.IO.DriveInfo In System.IO.DriveInfo.GetDrives()
Dim node As TreeNode = New TreeNode()

node.Value = drive.Name
If (drive.IsReady) Then
node.Text = drive.Name & _
" - (free space: " & drive.AvailableFreeSpace & ")"
LoadDirectories(node, drive.Name)
Else
node.Text = drive.Name & " - (not ready)"
End If
Me.TreeView1.Nodes.Add(node)
Next
End If
Me.TreeView1.CollapseAll()
End Sub
Private Sub LoadDirectories(ByVal parent As TreeNode, ByVal path As String)
Dim directory As System.IO.DirectoryInfo = _
New System.IO.DirectoryInfo(path)
Try
For Each d As System.IO.DirectoryInfo In directory.GetDirectories()
Dim node As TreeNode = New TreeNode(d.Name, d.FullName)
parent.ChildNodes.Add(node)
Continued
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Chapter 25: File I/O and Streams
’Recurse the current directory
LoadDirectories(node, d.FullName)
Next
Catch ex As System.UnauthorizedAccessException
parent.Text += " (Access Denied)"
Catch ex As System.IO.IOException

parent.Text += " (Unknown Error: " + ex.Message + ")"
End Try
End Sub
<
/script
>
C#
<
script runat="server"
>
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
foreach (System.IO.DriveInfo drive in System.IO.DriveInfo.GetDrives())
{
TreeNode node = new TreeNode();
node.Value = drive.Name;
if (drive.IsReady)
{
node.Text = drive.Name +
" - (free space: " + drive.AvailableFreeSpace + ")";
LoadDirectories(node, drive.Name);
}
else
node.Text = drive.Name + " - (not ready)";
this.TreeView1.Nodes.Add(node);
}
}
this.TreeView1.CollapseAll();

}
private void LoadDirectories(TreeNode parent, string path)
{
System.IO.DirectoryInfo directory = new System.IO.DirectoryInfo(path);
try
{
foreach (System.IO.DirectoryInfo d in directory.GetDirectories())
{
TreeNode node = new TreeNode(d.Name, d.FullName);
parent.ChildNodes.Add(node);
Continued
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Chapter 25: File I/O and Streams
//Recurs the current directory
LoadDirectories(node, d.FullName);
}
}
catch (System.UnauthorizedAccessException e)
{
parent.Text += " (Access Denied)";
}
catch (System.IO.IOException e)
{
parent.Text += " (Unknown Error: " + e.Message + ")";
}
}
<
/script
>

Figure 25-3 shows what the page should look like in the browser. You should now be able to browse the
directory tree, much as you do in Windows Explorer, by opening and closing the TreeView nodes.
Figure 25-3
Notice that the example continuously creates new instances of the
DirectoryInfo
class each time the
method executes in order to continue to enumerate the directory tree. You could also extend this example
by displaying some additional properties as part of the
Node
text, such as the
CreationTime
or
Attributes
.
To perform only a specific action, you don’t have to create an instance of the
DirectoryInfo
class. You
can simply use the static methods exposed by the
Directory
class. These methods allow you to create,
read properties from, and delete a directory. Rather than creating an object instance that represents a
specific path and exposes methods that act on that path, the static methods exposed by the
Directory
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Chapter 25: File I/O and Streams
class generally require you to pass the path as a method parameter. Listing 25-4 shows how you can use
the static methods exposed by the
Directory
class to create, read properties from, and delete a directory.

Remember to be very careful when deleting a folder from your hard drive. It is
possible to permanently delete important data from your system or change the
permissions of a resource, which would result in your losing the ability to access
the resource.
Listing 25-4: Working with the static methods of the Directory class
VB
<
%@ Import Namespace="System.IO" %
>
<
script runat="server"
>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Directory.CreateDirectory("C:
\
Wrox")
If Directory.Exists("C:
\
Wrox") Then
Me.Label1.Text = _
Directory.GetCreationTime("C:
\
Wrox").ToString()
Me.Label2.Text = _
Directory.GetLastAccessTime("C:
\
Wrox").ToString()
Me.Label3.Text = _
Directory.GetLastWriteTime("C:
\

Wrox").ToString()
Directory.Delete("C:
\
Wrox")
End If
End Sub
<
/script
>
<
html xmlns=" />>
<
head runat="server"
>
<
title
>
Using Static Methods
<
/title
>
<
/head
>
<
body
>
<
form id="form1" runat="server"
>

<
div
>
Creation Time:
<
asp:Label ID="Label1" runat="server" Text="Label"
><
/asp:Label
><
br /
>
Last Access Time:
<
asp:Label ID="Label2" runat="server" Text="Label"
><
/asp:Label
><
br /
>
Last Write Time:
<
asp:Label ID="Label3" runat="server" Text="Label"
><
/asp:Label
>
<
/div
>
<
/form

>
<
/body
>
<
/html
>
Continued
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Chapter 25: File I/O and Streams
C#
<
%@ Import Namespace="System.IO" %
>
<
script runat="server"
>
protected void Page_Load(object sender, EventArgs e)
{
Directory.CreateDirectory(@"C:
\
Wrox");
if (Directory.Exists(@"C:
\
Wrox") )
{
this.Label1.Text =
Directory.GetCreationTime(@"C:
\

Wrox").ToString();
this.Label2.Text =
Directory.GetLastAccessTime(@"C:
\
Wrox").ToString();
this.Label3.Text =
Directory.GetLastWriteTime(@"C:
\
Wrox").ToString();
Directory.Delete(@"C:
\
Wrox");
}
}
<
/script
>
When you load this page in the browser, you will see that the
Creation Time, Last Access Time
,and
Last Write Time
are displayed. Additionally, if you open Windows Explorer, you will see that the Wrox
directory has been deleted.
Using Relative Paths and Setting and Getting the Current Directory
When an ASP.NET page is e xecuted, the thread used to execute the code that generates the page, by
default,hasacurrentworkingdirectory.Itusesthisdirectory as its base directory if you have specified
relative paths in your application. Therefore, if you pass a relative filename into any
System.IO
class, the
file is assumed to be located in the current working directory.

For example, the default working directory for the ASP.NET Development Server is a directory under
your Visual Studio install root. If you installed Visual Studio in
C:
\
Program Files
,yourASP.NET
Development Server working directory would be
c:
\
Program Files
\
Microsoft Visual Studio 9.0
\
Common7
\
IDE
.
You can find the location of your working directory by using the
Directory
class’s
GetCurrentDirec-
tory()
method. In addition, you can change the current working directory using the
Directory
class’s
SetCurrentDirectory()
method.
Listing 25-5 shows you how to set and then display your working directory.
Listing 25-5: Setting and displaying the application’s working directory
VB

<
%@ Import Namespace="System.IO" %
>
<
script runat="server"
>
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Chapter 25: File I/O and Streams
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Me.Label1.Text = Directory.GetCurrentDirectory()
Directory.SetCurrentDirectory("C:
\
Wrox")
Me.Label2.Text = Directory.GetCurrentDirectory()
End Sub
<
/script
>
<
html xmlns=" />>
<
head runat="server"
>
<
title
>
Set and Display the Working Directory
<
/title

>
<
/head
>
<
body
>
<
form id="form1" runat="server"
>
<
div
>
Old Working Directory:
<
asp:Label ID="Label1" runat="server" Text="Label"
><
/asp:Label
><
br /
>
New Working Directory:
<
asp:Label ID="Label2" runat="server" Text="Label"
><
/asp:Label
>
<
/div
>

<
/form
>
<
/body
>
<
/html
>
C#
<
script runat="server"
>
protected void Page_Load(object sender, EventArgs e)
{
this.Label1.Text = Directory.GetCurrentDirectory();
Directory.SetCurrentDirectory(@"C:
\
Wrox");
this.Label2.Text = Directory.GetCurrentDirectory();
}
<
/script
>
Note that the directory parameter you specify in the
SetCurrentDirectory()
method must already
exist; otherwise, ASP.NET throws an exception. Knowing this, it would probably be a good idea to use
the
Exists()

method of the
Directory
class to make sure the directory you are specifying does, in fact,
already exist before you try to change the working directory.
When you execute this code, you should see that it displays the original working directory, and then
displays the new working directory after you change it. Figure 25-4 shows what the page looks like when
executed.
File and FileInfo
Now that you can effectively display and browse a directory tree, you can expand the example even fur-
ther by displaying the files located in the directory that is currently selected in your TreeView
control.
The simplest way to display the files is to bind a
FileInfo
array to a
GridView
. This example uses the
GetFiles()
method of the
DirectoryInfo
class because it returns an array of
FileInfo
objects. You
want to use this method because the
FileInfo
object enables you to display some properties of each
1149