HierarchicalDataSourceView.Select HierarchicalDataSourceView.Select HierarchicalDataSourceView.Select HierarchicalDataSourceView.Select Method

Definition

Ruft eine Liste aller Datenelemente in der Ansicht ab.Gets a list of all the data items in the view.

public:
 abstract System::Web::UI::IHierarchicalEnumerable ^ Select();
public abstract System.Web.UI.IHierarchicalEnumerable Select ();
abstract member Select : unit -> System.Web.UI.IHierarchicalEnumerable
Public MustOverride Function Select () As IHierarchicalEnumerable

Gibt zurück

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie die Select -Methode in einer Klasse überschrieben wird HierarchicalDataSourceView , die von der FileSystemInfo -Klasse abgeleitet wird, um hierarchische Daten aus einem Dateisystem abzurufen.The following code example demonstrates how to override the Select method in a class that derives from the HierarchicalDataSourceView class to retrieve hierarchical FileSystemInfo data from a file system. Aus Sicherheitsgründen werden Dateisystem Informationen nur angezeigt, wenn das Datenquellen-Steuerelement in einem localhost-, authentifizierten Szenario verwendet wird und nur mit dem virtuellen Verzeichnis gestartet wird, in dem sich die Web Forms Seite mit dem Datenquellen-Steuerelement befindet.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. Andernfalls kann der viewPath -Parameter, der an den Konstruktor des View-Objekts übergeben wird, zum Erstellen einer Sicht verwendet werden, die auf dem aktuellen Dateisystempfad basiert.Otherwise, the viewPath parameter passed to the constructor of the view object might be used to create a view based on the current file system path. Dieses Codebeispiel ist Teil eines größeren Beispiels, das für die HierarchicalDataSourceControl -Klasse bereitgestellt wird.This code example is part of a larger example provided for the HierarchicalDataSourceControl class.

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.");
        }
    }
}
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 'New


    ' 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 'FileSystemDataSourceView

Hinweise

Die Select -Methode gibt IHierarchicalEnumerable eine Auflistung von Datenelementen in der aktuellen Ansicht zurück.The Select method returns an IHierarchicalEnumerable collection of data items in the current view. Sie können die GetEnumerator -Methode zum Abrufen eines IEnumerator Objekts und durchlaufen der Auflistung von Datenelementen abrufen.You can call the GetEnumerator method to get an IEnumerator object and iterate through the collection of data items.

Gilt für:

Siehe auch