IWebPartRow Interface


Defines a provider interface for connecting two server controls using a single field of data.

Namespace:   System.Web.UI.WebControls.WebParts
Assembly:  System.Web (in System.Web.dll)

Public Interface IWebPartRow


Gets the schema information for a data row that is used to share data between two WebPart controls.


Returns the data for the row that is being used by the interface as the basis of a connection between two WebPart controls.

This interface is designed to be used with Web Parts connections. In a Web Parts connection, two server controls that reside in a WebPartZoneBase zone establish a connection and share data, with one control acting as the consumer and the other control acting as a provider. The mechanism for sharing data in a Web Parts connection is an interface instance, which the provider serves to the consumer by means of a callback method. To establish a connection, the consumer and provider must both work with the same interface type for sharing data. If the consumer does not recognize the interface type sent by the provider, it is still possible to connect the controls by means of a transformer (a WebPartTransformer object) that translates the interface instance sent by the provider into a type that the consumer recognizes. For details on connections, see WebPartConnection and Web Parts Connections Overview.

The IWebPartRow interface is a provider interface included with the Web Parts control set as a standard interface for creating connections based on a data row. You can also create custom interfaces to use with Web Parts connections, but in many data-driven Web applications, it is useful to create connections based on a common field (for details, see the IWebPartField interface), table (for details, see the IWebPartTable interface), or row from the data source. In a typical connection, a WebPart control acting as a provider would implement the IWebPartRow interface and provide an instance of the interface to consumers in a special callback method. For example, the provider might implement an IWebPartRow interface for a row that corresponds to a user in your user information table. Another WebPart control acting as a consumer would define a special method to receive the interface instance, and could then extract the user data, use it to look up additional information about that user's accounts, and display all the information related to that user on the page.

The IWebPartRow interface has two exposed members. The Schema property returns schema information about the data row encapsulated in a PropertyDescriptorCollection object. The GetRowData method declares a method that an implementer (such as a provider control) uses to retrieve the interface instance's row data when the callback method is invoked.

The following code example demonstrates how to create a static connection between two controls using the IWebPartRow interface. The code example has three parts:

  • Source code for two custom WebPart controls that can form a connection using the IWebPartRow interface, with one control acting as the provider, and the other acting as the consumer.

  • A Web page that hosts the controls and declares the static connection in persistence format.

  • A description of what happens when the example code runs.

The first part of the code example is the source code for the two custom controls. First is the code for the provider, which implements the IWebPartRow interface. For simplicity in the example, the provider creates a table with some data rather than connecting to a database. The GetConnectionInterface method serves as the provider's connection point, the callback method that returns the interface instance to the consumer. As for the consumer, it retrieves the interface instance from the provider in its method named SetConnectionInterface, which is marked with a ConnectionConsumer attribute. After retrieving the instance of the interface, the consumer, in its OnPreRender method, calls the implementation of the GetRowData method in the provider, to retrieve the actual data and write it to the page.

For the code example to run, you must compile this source code. You can compile it explicitly and put the resulting assembly in your Web site's Bin folder or the global assembly cache. Alternatively, you can put the source code in your site's App_Code folder, where it will be dynamically compiled at run time. This code example uses dynamic compilation. For a walkthrough that demonstrates how to compile, see Walkthrough: Developing and Using a Custom Web Server Control.

Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Data
Imports System.Reflection
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts

Namespace Samples.AspNet.VB.Controls

  ' This sample code creates a Web Parts control that acts as a provider 
  ' of row data.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public NotInheritable Class RowProviderWebPart
    Inherits WebPart
    Implements IWebPartRow
    Private _table As DataTable

    Public Sub New()
      _table = New DataTable()

      Dim col As New DataColumn()
      col.DataType = GetType(String)
      col.ColumnName = "Name"

      col = New DataColumn()
      col.DataType = GetType(String)
      col.ColumnName = "Address"

      col = New DataColumn()
      col.DataType = GetType(Integer)
      col.ColumnName = "ZIP Code"

      Dim row As DataRow = _table.NewRow()
      row("Name") = "John Q. Public"
      row("Address") = "123 Main Street"
      row("ZIP Code") = 98000

    End Sub 'NewNew

    <ConnectionProvider("Row")> _
    Public Function GetConnectionInterface() As IWebPartRow
      Return New RowProviderWebPart()

    End Function 'GetConnectionInterface

    Public ReadOnly Property Schema() As _
      ComponentModel.PropertyDescriptorCollection Implements IWebPartRow.Schema

        Return TypeDescriptor.GetProperties(_table.DefaultView(0))
      End Get

    End Property

    Public Sub GetRowData(ByVal callback As RowCallback) _
      Implements IWebPartRow.GetRowData

    End Sub

  End Class 'RowProviderWebPart 

  ' This sample code creates a Web Parts control that acts as a consumer 
  ' of row data.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public NotInheritable Class RowConsumerWebPart
    Inherits WebPart
    Private _provider As IWebPartRow
    Private _tableData As ICollection

    Private Sub GetRowData(ByVal rowData As Object)
      _tableData = CType(rowData, ICollection)

    End Sub

    Protected Overrides Sub OnPreRender(ByVal e As EventArgs)

      If Not (_provider Is Nothing) Then
        _provider.GetRowData(New RowCallback(AddressOf GetRowData))
      End If

    End Sub

    Protected Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)

      If Not (_provider Is Nothing) Then
        Dim props As PropertyDescriptorCollection = _provider.Schema
        Dim count As Integer = 0
        If Not (props Is Nothing) AndAlso props.Count > 0 _
          AndAlso Not (_tableData Is Nothing) Then

          Dim prop As PropertyDescriptor
          For Each prop In props
            Dim o As DataRow
            For Each o In _tableData
              writer.Write(prop.DisplayName & ": " & o(count))
              count = count + 1
            Next o
          Next prop
          writer.Write("No data")
        End If
        writer.Write("Not connected")
      End If

    End Sub

    <ConnectionConsumer("Row")> _
    Public Sub SetConnectionInterface(ByVal provider As IWebPartRow)
      _provider = provider

    End Sub

  End Class 'RowConsumerWebPart 

End Namespace  ' Samples.AspNet.VB.Controls 

The second part of the code example is the Web page that declares the static connection and hosts the controls. Near the top of the page is a Register directive that declares the namespace of the source code contained in the App_Code directory. The connection is declared using an <asp:webpartconnection> element. The custom consumer and provider controls are declared in a <zonetemplate> element within an <asp:webpartzone> element, which is required for them to be able to connect (they must reside within a zone that inherits from the WebPartZoneBase class).

<%@ page language="VB" %>
<%@ Register tagprefix="IRow" 
    Namespace="Samples.AspNet.VB.Controls" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>IRow Test Page</title>
    <form id="form1" runat="server">
      <asp:webpartmanager ID="WebPartManager1" runat="server">
          <asp:webpartconnection ID="wp1" ProviderID="provider1" 

        <asp:webpartzone ID="WebPartZone1" runat="server">
            <irow:RowProviderWebPart ID="provider1" runat="server" 
              Title="Row Provider Control" />
            <irow:RowConsumerWebPart ID="consumer1" runat="server" 
              Title="Row Consumer Control" />

Load the page in a browser. The consumer control displays the data provided from the specified row, which the provider makes available through an instance of the IWebPartRow interface.

.NET Framework
Available since 2.0
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