HierarchicalDataSourceView.Select 方法

定义

获取视图中所有数据项的列表。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

返回

数据项的 IHierarchicalEnumerable 集合。An IHierarchicalEnumerable collection of data items.

示例

下面的代码示例演示如何在从Select HierarchicalDataSourceView类派生的类中重写方法, 以从文件系统FileSystemInfo中检索分层数据。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. 出于安全目的, 仅当数据源控件正用于本地主机和身份验证方案时才会显示文件系统信息, 并且仅从使用数据源控件的 Web 窗体页所在的虚拟目录开始。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. 否则, viewPath传递给 view 对象的构造函数的参数可能用于基于当前文件系统路径创建视图。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. 此代码示例是为HierarchicalDataSourceControl类提供的更大示例的一部分。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


    ' 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

注解

方法返回当前视图中数据项的集合。IHierarchicalEnumerable SelectThe Select method returns an IHierarchicalEnumerable collection of data items in the current view. 您可以调用GetEnumerator方法来IEnumerator获取对象并循环访问数据项的集合。You can call the GetEnumerator method to get an IEnumerator object and iterate through the collection of data items.

适用于

另请参阅