HierarchicalDataSourceView Class
Definition
Important
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Represents a data view on a node or collection of nodes in a hierarchical data structure for a HierarchicalDataSourceControl control.
public ref class HierarchicalDataSourceView abstractpublic abstract class HierarchicalDataSourceViewtype HierarchicalDataSourceView = classPublic MustInherit Class HierarchicalDataSourceView- Inheritance
-
HierarchicalDataSourceView
- Derived
Examples
The following code example demonstrates how to derive a class from the HierarchicalDataSourceView class to retrieve data from hierarchical data storage, in this case a file system. The FileSystemDataSourceView class is a strongly typed HierarchicalDataSourceView instance that enables hierarchical Web server controls such as the TreeView control to bind to a FileSystemDataSource control and display file system information. 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. Otherwise, the viewPath parameter passed to the constructor might be used to create a view based on the current file system path. 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
Remarks
ASP.NET supports a 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 that 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 abstract HierarchicalDataSourceControl class. You can think of a data source control as the combination of the data source control object and its associated views on the underlying data, which are represented by data source view objects. Hierarchical data source controls support a hierarchical data source view for each hierarchical level of data they represent. The data source views are not named, like the DataSourceView objects associated with a DataSourceControl control, but are identified by their unique hierarchical path.
Data source views define the capabilities of a data source control. All data source view objects, including HierarchicalDataSourceView, support data retrieval from the underlying data source using the Select method, which retrieves a hierarchical list of data as an IHierarchicalEnumerable object. All data source view objects optionally support a basic set of capabilities, including operations such as Insert, Update, Delete, and sorting. A data-bound control can discover the capabilities of a data source control by retrieving an associated data source view using the GetHierarchicalView method and querying the view at design time or at run time. HierarchicalDataSourceView does not currently support Insert, Update or Delete operations.
Notes to Implementers
When you inherit from HierarchicalDataSourceView, you must override the following member: Select().
Constructors
| HierarchicalDataSourceView() |
Initializes a new instance of the HierarchicalDataSourceView class. |
Methods
| Equals(Object) |
Determines whether the specified object is equal to the current object. (Inherited from Object) |
| GetHashCode() |
Serves as the default hash function. (Inherited from Object) |
| GetType() |
Gets the Type of the current instance. (Inherited from Object) |
| MemberwiseClone() |
Creates a shallow copy of the current Object. (Inherited from Object) |
| Select() |
Gets a list of all the data items in the view. |
| ToString() |
Returns a string that represents the current object. (Inherited from Object) |
