HierarchicalDataSourceControl Class

Definition

public ref class HierarchicalDataSourceControl abstract : System::Web::UI::Control, System::Web::UI::IHierarchicalDataSource

[System.ComponentModel.Bindable(false)]
public abstract class HierarchicalDataSourceControl : System.Web.UI.Control, System.Web.UI.IHierarchicalDataSource

[<System.ComponentModel.Bindable(false)>]
type HierarchicalDataSourceControl = class
    inherit Control
    interface IHierarchicalDataSource

Public MustInherit Class HierarchicalDataSourceControl
Inherits Control
Implements IHierarchicalDataSource

Inheritance

Object

Control

HierarchicalDataSourceControl

Derived

System.Web.UI.WebControls.SiteMapDataSource

System.Web.UI.WebControls.XmlDataSource

Attributes

BindableAttribute

Implements

IHierarchicalDataSource

Examples

The following code example demonstrates how to extend the abstract HierarchicalDataSourceControl class and the HierarchicalDataSourceView class, and implement the IHierarchicalEnumerable and IHierarchyData interfaces to create a hierarchical data source control that retrieves file system information. The FileSystemDataSource control enables Web server controls to bind to FileSystemInfo objects and display basic file system information. The FileSystemDataSource class in the example provides the implementation of the GetHierarchicalView method, which retrieves a FileSystemDataSourceView object. The FileSystemDataSourceView object retrieves the data from the underlying data storage, in this case the file system information on the Web server. For security purposes, file system information is displayed only if the data source control is being used in a localhost, authenticated scenario, and only starts with the virtual directory that the Web Forms page using the data source control resides in. Finally, two classes that implement IHierarchicalEnumerable and IHierarchyData are provided to wrap the FileSystemInfo objects that FileSystemDataSource uses.

using System;
using System.Collections;
using System.IO;
using System.Runtime.InteropServices;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public class FileSystemDataSource :
    HierarchicalDataSourceControl, IHierarchicalDataSource
{
    private FileSystemDataSourceView view = null;

    public FileSystemDataSource() : base() { }

    protected override HierarchicalDataSourceView
        GetHierarchicalView(string viewPath)
    {
        view = new FileSystemDataSourceView(viewPath);
        return view;
    }
}
public class FileSystemDataSourceView : HierarchicalDataSourceView
{
    private string _viewPath;

    public FileSystemDataSourceView(string viewPath)
    {
        HttpRequest currentRequest = HttpContext.Current.Request;
        if (viewPath == "")
        {
            _viewPath = currentRequest.MapPath(currentRequest.ApplicationPath);
        }
        else
        {
            _viewPath = Path.Combine(
                currentRequest.MapPath(currentRequest.ApplicationPath),
                viewPath);
        }
    }

    // Starting with the rootNode, recursively build a list of
    // FileSystemInfo nodes, create FileSystemHierarchyData
    // objects, add them all to the FileSystemHierarchicalEnumerable,
    // and return the list.
    public override IHierarchicalEnumerable Select()
    {
        HttpRequest currentRequest = HttpContext.Current.Request;

        // SECURITY: There are many security issues that can be raised
        // SECURITY: by exposing the file system structure of a Web server
        // SECURITY: to an anonymous user in a limited trust scenario such as
        // SECURITY: a Web page served on an intranet or the Internet.
        // SECURITY: For this reason, the FileSystemDataSource only
        // SECURITY: shows data when the HttpRequest is received
        // SECURITY: from a local Web server. In addition, the data source
        // SECURITY: does not display data to anonymous users.
        if (currentRequest.IsAuthenticated &&
            (currentRequest.UserHostAddress == "127.0.0.1" ||
             currentRequest.UserHostAddress == "::1"))
        {
            DirectoryInfo rootDirectory = new DirectoryInfo(_viewPath);
            if (!rootDirectory.Exists)
            {
                return null;
            }

            FileSystemHierarchicalEnumerable fshe =
                new FileSystemHierarchicalEnumerable();

            foreach (FileSystemInfo fsi
                in rootDirectory.GetFileSystemInfos())
            {
                fshe.Add(new FileSystemHierarchyData(fsi));
            }
            return fshe;
        }
        else
        {
            throw new NotSupportedException(
                "The FileSystemDataSource only " +
                "presents data in an authenticated, localhost context.");
        }
    }
}
// A collection of FileSystemHierarchyData objects
public class FileSystemHierarchicalEnumerable :
    ArrayList, IHierarchicalEnumerable
{
    public FileSystemHierarchicalEnumerable()
        : base()
    {
    }

    public IHierarchyData GetHierarchyData(object enumeratedItem)
    {
        return enumeratedItem as IHierarchyData;
    }
}

public class FileSystemHierarchyData : IHierarchyData
{
    private FileSystemInfo fileSystemObject = null;

    public FileSystemHierarchyData(FileSystemInfo obj)
    {
        fileSystemObject = obj;
    }

    public override string ToString()
    {
        return fileSystemObject.Name;
    }
    // IHierarchyData implementation.
    public bool HasChildren
    {
        get
        {
            if (typeof(DirectoryInfo) == fileSystemObject.GetType())
            {
                DirectoryInfo temp = (DirectoryInfo)fileSystemObject;
                return (temp.GetFileSystemInfos().Length > 0);
            }
            else
            {
                return false;
            }
        }
    }
    // DirectoryInfo returns the OriginalPath, while FileInfo returns
    // a fully qualified path.
    public string Path
    {
        get
        {
            return fileSystemObject.ToString();
        }
    }
    public object Item
    {
        get
        {
            return fileSystemObject;
        }
    }
    public string Type
    {
        get
        {
            return "FileSystemData";
        }
    }
    public IHierarchicalEnumerable GetChildren()
    {
        FileSystemHierarchicalEnumerable children =
            new FileSystemHierarchicalEnumerable();

        if (typeof(DirectoryInfo) == fileSystemObject.GetType())
        {
            DirectoryInfo temp = (DirectoryInfo)fileSystemObject;
            foreach (FileSystemInfo fsi in temp.GetFileSystemInfos())
            {
                children.Add(new FileSystemHierarchyData(fsi));
            }
        }
        return children;
    }

    public IHierarchyData GetParent()
    {
        FileSystemHierarchicalEnumerable parentContainer =
            new FileSystemHierarchicalEnumerable();

        if (typeof(DirectoryInfo) == fileSystemObject.GetType())
        {
            DirectoryInfo temp = (DirectoryInfo)fileSystemObject;
            return new FileSystemHierarchyData(temp.Parent);
        }
        else if (typeof(FileInfo) == fileSystemObject.GetType())
        {
            FileInfo temp = (FileInfo)fileSystemObject;
            return new FileSystemHierarchyData(temp.Directory);
        }
        // If FileSystemObj is any other kind of FileSystemInfo, ignore it.
        return null;
    }
}

Imports System.Collections
Imports System.IO
Imports System.Runtime.InteropServices
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet

    Public Class FileSystemDataSource
        Inherits HierarchicalDataSourceControl

        Public Sub New()
        End Sub

        Private view As FileSystemDataSourceView = Nothing

        Protected Overrides Function GetHierarchicalView( _
            ByVal viewPath As String) As HierarchicalDataSourceView

            view = New FileSystemDataSourceView(viewPath)
            Return view
        End Function

    End Class
    Public Class FileSystemDataSourceView
        Inherits HierarchicalDataSourceView

        Private _viewPath As String

        Public Sub New(ByVal viewPath As String)
            Dim currentRequest As HttpRequest = HttpContext.Current.Request
            If viewPath = "" Then
                _viewPath = currentRequest.MapPath(currentRequest.ApplicationPath)
            Else
                _viewPath = Path.Combine(currentRequest.MapPath(currentRequest.ApplicationPath), viewPath)
            End If
        End Sub


        ' Starting with the rootNode, recursively build a list of
        ' FileSystemInfo nodes, create FileSystemHierarchyData
        ' objects, add them all to the FileSystemHierarchicalEnumerable,
        ' and return the list.
        Public Overrides Function [Select]() As IHierarchicalEnumerable
            Dim currentRequest As HttpRequest = HttpContext.Current.Request

            ' SECURITY: There are many security issues that can be raised
            ' SECURITY: by exposing the file system structure of a Web server
            ' SECURITY: to an anonymous user in a limited trust scenario such as
            ' SECURITY: a Web page served on an intranet or the Internet.
            ' SECURITY: For this reason, the FileSystemDataSource only
            ' SECURITY: shows data when the HttpRequest is received
            ' SECURITY: from a local Web server. In addition, the data source
            ' SECURITY: does not display data to anonymous users.
            If currentRequest.IsAuthenticated AndAlso _
                (currentRequest.UserHostAddress = "127.0.0.1" OrElse _
                 currentRequest.UserHostAddress = "::1") Then

                Dim rootDirectory As New DirectoryInfo(_viewPath)

                Dim fshe As New FileSystemHierarchicalEnumerable()

                Dim fsi As FileSystemInfo
                For Each fsi In rootDirectory.GetFileSystemInfos()
                    fshe.Add(New FileSystemHierarchyData(fsi))
                Next fsi
                Return fshe
            Else
                Throw New NotSupportedException( _
                    "The FileSystemDataSource only " + _
                    "presents data in an authenticated, localhost context.")
            End If
        End Function 'Select
    End Class

    Public Class FileSystemHierarchicalEnumerable
        Inherits ArrayList
        Implements IHierarchicalEnumerable

        Public Sub New()
        End Sub


        Public Overridable Function GetHierarchyData( _
            ByVal enumeratedItem As Object) As IHierarchyData _
            Implements IHierarchicalEnumerable.GetHierarchyData

            Return CType(enumeratedItem, IHierarchyData)
        End Function

    End Class


    Public Class FileSystemHierarchyData
        Implements IHierarchyData

        Public Sub New(ByVal obj As FileSystemInfo)
            fileSystemObject = obj
        End Sub

        Private fileSystemObject As FileSystemInfo = Nothing

        Public Overrides Function ToString() As String
            Return fileSystemObject.Name
        End Function

        ' IHierarchyData implementation.
        Public Overridable ReadOnly Property HasChildren() As Boolean _
         Implements IHierarchyData.HasChildren
            Get
                If GetType(DirectoryInfo) Is fileSystemObject.GetType() Then
                    Dim temp As DirectoryInfo = _
                        CType(fileSystemObject, DirectoryInfo)
                    Return temp.GetFileSystemInfos().Length > 0
                Else
                    Return False
                End If
            End Get
        End Property
        ' DirectoryInfo returns the OriginalPath, while FileInfo returns
        ' a fully qualified path.

        Public Overridable ReadOnly Property Path() As String _
         Implements IHierarchyData.Path
            Get
                Return fileSystemObject.ToString()
            End Get
        End Property

        Public Overridable ReadOnly Property Item() As Object _
         Implements IHierarchyData.Item
            Get
                Return fileSystemObject
            End Get
        End Property

        Public Overridable ReadOnly Property Type() As String _
         Implements IHierarchyData.Type
            Get
                Return "FileSystemData"
            End Get
        End Property

        Public Overridable Function GetChildren() _
            As IHierarchicalEnumerable _
            Implements IHierarchyData.GetChildren

            Dim children As New FileSystemHierarchicalEnumerable()

            If GetType(DirectoryInfo) Is fileSystemObject.GetType() Then
                Dim temp As DirectoryInfo = _
                    CType(fileSystemObject, DirectoryInfo)
                Dim fsi As FileSystemInfo
                For Each fsi In temp.GetFileSystemInfos()
                    children.Add(New FileSystemHierarchyData(fsi))
                Next fsi
            End If
            Return children
        End Function 'GetChildren


        Public Overridable Function GetParent() As IHierarchyData _
         Implements IHierarchyData.GetParent
            Dim parentContainer As New FileSystemHierarchicalEnumerable()

            If GetType(DirectoryInfo) Is fileSystemObject.GetType() Then
                Dim temp As DirectoryInfo = _
                    CType(fileSystemObject, DirectoryInfo)
                Return New FileSystemHierarchyData(temp.Parent)
            ElseIf GetType(FileInfo) Is fileSystemObject.GetType() Then
                Dim temp As FileInfo = CType(fileSystemObject, FileInfo)
                Return New FileSystemHierarchyData(temp.Directory)
            End If
            ' If FileSystemObj is any other kind of FileSystemInfo, ignore it.
            Return Nothing
        End Function 'GetParent
    End Class
End Namespace

The following code example demonstrates how to declaratively bind a TreeView control to file system data using the FileSystemDataSource example.

<%@ Page Language="C#" %>
<%@ Register Tagprefix="aspSample" Namespace="Samples.AspNet" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
        <form id="form1" runat="server">

            <asp:treeview
                id="TreeView1"
                runat="server"
                datasourceid="FileSystemDataSource1" />            

            <aspSample:filesystemdatasource
                id = "FileSystemDataSource1"
                runat = "server" />            

        </form>
    </body>
</html>

<%@ Page Language="VB" %>
<%@ Register Tagprefix="aspSample" Namespace="Samples.AspNet" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
        <form id="form1" runat="server">

            <asp:treeview
                id="TreeView1"
                runat="server"
                datasourceid="FileSystemDataSource1" />            

            <aspSample:filesystemdatasource
                id = "FileSystemDataSource1"
                runat = "server" />            

        </form>
    </body>
</html>

Remarks

ASP.NET supports a controls data-binding architecture that enables Web server controls to bind to data and present it in a consistent fashion. Web server controls that bind to data are called data-bound controls, and the classes that facilitate binding are called data source controls. Data source controls can represent any data source: a file, a stream, a relational database, a business object, and so on. Data source controls present data in a consistent way to data-bound controls, regardless of the source or format of the underlying data.

Data source controls that represent hierarchical data derive from the HierarchicalDataSourceControl class, while data source controls that represent lists or tables of data derive from the DataSourceControl class. The HierarchicalDataSourceControl class is the base implementation of the IHierarchicalDataSource interface, which defines a single method to retrieve hierarchical data source view objects associated with the data source control, GetHierarchicalView.

You can think of a data source control as the combination of the HierarchicalDataSourceControl object and its associated views on the underlying data, called data source view objects. While data source controls that represent tabular data are typically associated with only one named view, the HierarchicalDataSourceControl class supports a data source view for each level of hierarchical data that the data source control represents. The level of hierarchical data is identified by a unique hierarchical path, passed to the GetHierarchicalView method in the viewPath parameter. Each HierarchicalDataSourceView object defines the capabilities of a data source control for the hierarchical level represented, and performs operations such as insert, update, delete, and sort.

Web server controls that derive from the HierarchicalDataBoundControl class, such as TreeView, use hierarchical data source controls to bind to hierarchical data.

Data source controls are implemented as controls to enable declarative persistence and to optionally permit participation in state management. Data source controls have no visual rendering, and therefore do not support themes.

Constructors

Properties

Methods

Events

Explicit Interface Implementations

Extension Methods

Applies to

See also

• IHierarchicalDataSource
• DataSourceControl