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

Definizione

Ottiene un elenco di tutti gli elementi di dati presenti nella visualizzazione.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

Restituisce

Esempi

Il codice seguente viene illustrato come eseguire l'override di Select metodo in una classe che deriva dal HierarchicalDataSourceView classe da cui recuperare gerarchici FileSystemInfo i dati da un file system.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. Per motivi di sicurezza, informazioni sul file system viene visualizzate solo se il controllo origine dati utilizzato in un host locale, uno scenario autenticato e viene avviato solo con la directory virtuale che risiede la pagina Web Form tramite il controllo origine dati.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. In caso contrario, il viewPath parametro passato al costruttore dell'oggetto vista può essere usato per creare una visualizzazione basata sul percorso del file system corrente.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. Questo esempio di codice è parte di un esempio più esaustivo disponibile per il HierarchicalDataSourceControl classe.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

Commenti

Il Select metodo restituisce un IHierarchicalEnumerable raccolta di elementi di dati nella visualizzazione corrente.The Select method returns an IHierarchicalEnumerable collection of data items in the current view. È possibile chiamare il GetEnumerator metodo per ottenere un IEnumerator dell'oggetto e scorrere la raccolta di elementi di dati.You can call the GetEnumerator method to get an IEnumerator object and iterate through the collection of data items.

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