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

Wor king with Drives, Directories, and F ilesMany times in your ASP.NET applications, you need to interact with the local file system, reading directory structures, reading and writing t

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Wor king with Drives, Directories, and F iles

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 TheSystem.IO

namespace within the NET Framework makes working with file system directories and files very easy

While working with the classes in theSystem.IOnamespace, 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 theSystem.IOnamespace at the top of the directory tree by using a great

new addition to the NET 3.5 class libraries, theDriveInfoclass This class supplements the

GetLog-icalDrives()method of theDirectoryclass 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 aDriveInfoobject 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="http://www.w3.org/1999/xhtml" >

<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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<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#

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 theDriveTypeenumeration 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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You can also enumerate through all the drives on the local file system by using theDriveInfo’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

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>

<title>Enumerate Local System Drives</title>

</head>

<body>

<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#

{

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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’sIsReadyproperty 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 TheSystem.IOnamespace contains two classes for working with file system

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directories, theDirectoryandDirectoryInfoclasses TheDirectoryclass exposes static methods you

can use to create, move, and delete directories TheDirectoryInforepresents a specific directory and

lets you perform many of the same actions as theDirectoryclass on the specific directory Additionally,

it enumerates child directories and files

To continue the example, you can use theGetDirectories()method of theDirectoryInfoclass 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

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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’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#

{

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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//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 theDirectoryInfoclass 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 Nodetext, such as theCreationTime

orAttributes

To perform only a specific action, you don’t have to create an instance of theDirectoryInfoclass You

can simply use the static methods exposed by theDirectoryclass 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 theDirectory

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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 theDirectoryclass 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" %>

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>

<title>Using Static Methods</title>

</head>

<body>

<div>

Creation Time:

<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label><br />

Last Access Time:

Last Write Time:

<asp:Label ID="Label3" runat="server" Text="Label"></asp:Label>

</div>

</form>

</body>

</html>

Continued

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{

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 theCreation Time, Last Access Time, and

Last Write Timeare 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 executed, the thread used to execute the code that generates the page, by

default, has a current working directory It uses this directory as its base directory if you have specified

relative paths in your application Therefore, if you pass a relative filename into anySystem.IOclass, 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 inC:\Program Files, your ASP.NET

Development Server working directory would bec:\Program Files\Microsoft Visual Studio 9.0\

Common7\IDE

You can find the location of your working directory by using theDirectoryclass’s

GetCurrentDirec-tory()method In addition, you can change the current working directory using theDirectoryclass’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

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Me.Label1.Text = Directory.GetCurrentDirectory() Directory.SetCurrentDirectory("C:\Wrox")

Me.Label2.Text = Directory.GetCurrentDirectory() End Sub

</script>

<title>Set and Display the Working Directory</title>

</head>

<body>

<div>

Old Working Directory:

New Working Directory:

<asp:Label ID="Label2" runat="server" Text="Label"></asp:Label>

</div>

</form>

</body>

</html>

C#

{

this.Label1.Text = Directory.GetCurrentDirectory();

Directory.SetCurrentDirectory(@"C:\Wrox");

this.Label2.Text = Directory.GetCurrentDirectory();

}

</script>

Note that the directory parameter you specify in theSetCurrentDirectory()method must already

exist; otherwise, ASP.NET throws an exception Knowing this, it would probably be a good idea to use theExists()method of theDirectoryclass 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 aFileInfoarray to aGridView This example uses the

GetFiles()method of theDirectoryInfoclass because it returns an array ofFileInfoobjects You

want to use this method because theFileInfoobject enables you to display some properties of each

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