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IHierarchicalDataSource Interface

  • Reference

Definition

Namespace:
System.Web.UI
Assembly:
System.Web.dll

Represents a hierarchical data source that hierarchical data-bound controls such as TreeView can bind to.

public interface class IHierarchicalDataSource
public interface IHierarchicalDataSource
type IHierarchicalDataSource = interface
Public Interface IHierarchicalDataSource
Derived

Examples

The following code example demonstrates how to extend the abstract HierarchicalDataSourceControl class, which implements the IHierarchicalDataSource interface, to create a data source control that displays file system information. The FileSystemDataSource class provides an implementation of the GetHierarchicalView method, which retrieves a strongly typed view object for a specified file system path. This code example is part of a larger example provided for the HierarchicalDataSourceControl class.

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;
    }
}

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

Remarks

ASP.NET supports a control 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, which is the base ASP.NET implementation of the IHierarchicalDataSource interface. The IHierarchicalDataSource interface is used to define data source controls that expose hierarchical data, rather than tabular or list-style data, to Web server controls that derive from the HierarchicalDataBoundControl class, such as the TreeView control. The interface defines a single method, GetHierarchicalView, which retrieves a strongly typed HierarchicalDataSourceView object. Data source controls that implement this interface support a hierarchical view for each hierarchical level of data they represent. The data source views are not named, like DataSourceView objects, but are identified by their unique hierarchical path, which is the viewPath parameter passed to the GetHierarchicalView method.

You can think of a data source control as the combination of the IHierarchicalDataSource object and its associated views on the underlying data. Each associated HierarchicalDataSourceView object defines the capabilities of a data source control for the hierarchical level represented, and, like all ASP.NET data source view objects, performs operations such as insert, update, delete, and sort.

Data source controls that expose only hierarchical data, such as SiteMapDataSource, are derived from the HierarchicalDataSourceControl class. Other data source controls that expose their data as both hierarchical data and tabular data, such as XmlDataSource, are derived from HierarchicalDataSourceControl but implement the IDataSource and IListSource interfaces.

Methods

GetHierarchicalView(String)

Gets the view helper object for the IHierarchicalDataSource interface for the specified path.

Events

DataSourceChanged

Occurs when the data storage that the IHierarchicalDataSource interface represents has changed.

Applies to

See also