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VirtualDirectory Class

Represents a directory object in a virtual file or resource space.

Namespace: System.Web.Hosting
Assembly: System.Web (in system.web.dll)

'Declaration
Public MustInherit Class VirtualDirectory
	Inherits VirtualFileBase
'Usage
Dim instance As VirtualDirectory

public abstract class VirtualDirectory extends VirtualFileBase
public abstract class VirtualDirectory extends VirtualFileBase
Not applicable.

The VirtualDirectory class is the base class for objects that represent directories in a virtual file system. Typically, you would implement a descendent of the VirtualDirectory class for each VirtualPathProvider class descendent in your Web application.

Notes to Inheritors: When you inherit from the VirtualDirectory class, you must override the Children, Directories, and Files properties to return an object implementing the IEnumerable interface. If your virtual-directory structure contains moderate to large numbers of virtual resources, you should take care to minimize the system resources consumed when enumerating the virtual directory by calling the Children, Directories, or Files properties.

The following code example is a VirtualDirectory class implementation that returns virtual directory information stored in a DataSet object. This code works with the code examples for the VirtualPathProvider and VirtualFile classes to provide virtual resources from a data store that is loaded into a DataSet object. For the complete instructions for compiling and running the example, see the Example section of the VirtualPathProvider class overview.

This example has two parts, the VirtualDirectory class implementation and the XML data file used to populate the DataSet object.

The first code example is an implementation of the VirtualDirectory class. In the constructor it uses a method on a custom VirtualPathProvider object to return a DataSet object. It then searches the DataSet object to retrieve the directory information associated with the virtual path provided.

Imports Microsoft.VisualBasic

Imports System
Imports System.Data
Imports System.Collections
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.Hosting


Namespace Samples.AspNet.VB
  <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal), _
   AspNetHostingPermission(SecurityAction.InheritanceDemand, level:=AspNetHostingPermissionLevel.Minimal)> _
  Public Class SampleVirtualDirectory
    Inherits VirtualDirectory

    Private spp As SamplePathProvider

    ' Declare the variable the property uses.
    Private existsValue As Boolean

    Public ReadOnly Property exists() As Boolean
      Get
        Return existsValue
      End Get
    End Property

    Public Sub New(ByVal virtualDir As String, ByVal provider As SamplePathProvider)
      MyBase.New(virtualDir)
      spp = provider
      GetData()
    End Sub

    Protected Sub GetData()
      ' Get the data from the SamplePathProvider.
      Dim spp As SamplePathProvider
      spp = CType(HostingEnvironment.VirtualPathProvider, SamplePathProvider)

      Dim ds As DataSet
      ds = spp.GetVirtualData

      ' Clean up the path to match data in resource file.
      Dim path As String
      path = VirtualPath.Replace(HostingEnvironment.ApplicationVirtualPath, "")
      Dim trimChars() As Char = {"/"c}
      path = path.TrimEnd(trimChars)

      ' Get the virtual directory from the resource table.
      Dim dirs As DataTable
      dirs = ds.Tables("resource")
      Dim rows As DataRow()
      rows = dirs.Select( _
        String.Format("(name = '{0}') AND (type='dir')", path))

      ' If the select returned a row, the directory exits.
      If (rows.Length > 0) Then
        existsValue = True

        ' Get the children from the resource table.
        ' This technique works for small numbers of virtual resources.
        '  Sites with moderate to large numbers of virtual
        '  resources should choose a method that consumes fewer
        '  computer resources.
        Dim childRows As DataRow()
        childRows = dirs.Select( _
          String.Format("parentPath = '{0}'", path))

        For Each childRow As DataRow In childRows
          Dim childPath As String
          childPath = CType(childRow("path"), String)

          If (childRow("type").ToString = "dir") Then
            Dim svd As New SampleVirtualDirectory(childPath, spp)
            childrenValue.Add(svd)
            directoriesValue.Add(svd)
          Else
            Dim svf As New SampleVirtualFile(childPath, spp)
            childrenValue.Add(svf)
            directoriesValue.Add(svf)
          End If
        Next

      End If
    End Sub

    Private childrenValue As ArrayList
    Public Overrides ReadOnly Property Children() As System.Collections.IEnumerable
      Get
        Return childrenValue
      End Get
    End Property

    Private directoriesValue As ArrayList
    Public Overrides ReadOnly Property Directories() As System.Collections.IEnumerable
      Get
        Return directoriesValue
      End Get
    End Property

    Private filesValue As ArrayList
    Public Overrides ReadOnly Property Files() As System.Collections.IEnumerable
      Get
        Return filesValue
      End Get
    End Property
  End Class

End Namespace

The second example is the XML data file used to populate the DataSet object returned by the custom VirtualPathProvider object. This XML data is used to demonstrate using the VirtualPathProvider, VirtualFile, and VirtualDirectory classes to retrieve data from external data, and is not intended to represent a production-quality data store.

<?xml version="1.0" encoding="utf-8" ?>
  <resource type="dir" 
    path="/vrDir" 
    parentPath="" 
    content="">
    <resource type="file" 
      path="/vrDir/Level1FileA.vrf"
      parentPath="/vrDir" 
      content="This is the content of file Level1FileA." >
    </resource>
    <resource type="file" 
      path="/vrDir/Level1FileB.vrf"
      parentPath="/vrDir" 
      content="This is the content of file Level1FileB.">
    </resource>
    <resource type="dir" 
      path="/vrDir/Level2DirA" 
      parentPath="/vrDir" 
      content="">
        <resource type="file" 
          path="/vrDir/Level2DirA/Level2FileA.vrf" 
          parentPath="/vrDir/Level2DirA" 
          content="This is the content of file Level2FileA." >
        </resource>
        <resource type="file" 
          path="/vrDir/Level2DirA/Level2FileB.vrf"
          parentPath="/vrDir/Level2DirA" 
          content="This is the content of file Level2FileB.">
        </resource>
    </resource>
    <resource type="dir" 
      path="/vrDir/Level2DirB" 
      parentPath="/vrDir" 
      content="">
      <resource type="file" 
        path="/vrDir/Level2DirB/Level2FileA.vrf" 
        parentPath="/vrDir/Level2DirB" 
        content="This is the content of file Level2FileA." >
      </resource>
      <resource type="file" 
        path="/vrDir/Level2DirB/Level2FileB.vrf"
        parentPath="/vrDir/Level2DirB" 
        content="This is the content of file Level2FileB.">
       </resource>
    </resource>
  </resource>

System.Object
   System.MarshalByRefObject
     System.Web.Hosting.VirtualFileBase
      System.Web.Hosting.VirtualDirectory

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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