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IWebPartTable Interface

Defines a provider interface for connecting two server controls using an entire table of data.

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

public interface IWebPartTable

The IWebPartTable type exposes the following members.

  NameDescription
Public propertySchemaGets the schema information for a data table that is used to share data between two WebPart controls.
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  NameDescription
Public methodGetTableDataReturns the data for the table that is being used by the interface as the basis of a connection between two WebPart controls.
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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 IWebPartTable interface is a provider interface included with the Web Parts control set as a standard interface for creating connections based on a data table. 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), row (for details, see the IWebPartRow interface), or table from the data source. In a typical connection, a WebPart control acting as a provider would implement the IWebPartTable interface and provide an instance of the interface to consumers in a special callback method. For example, the provider might implement an IWebPartTable interface for a table that contains financial performance data. Another WebPart control acting as a consumer would define a special method to receive the interface instance, and could then extract the data and render a chart to display the resulting information.

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

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

  • Source code for two custom WebPart controls that can form a connection using the IWebPartTable 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 IWebPartTable 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 GetTableData 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.

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

namespace Samples.AspNet.CS.Controls
{
  // This sample code creates a Web Parts control that acts as a provider  
  // of table data.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]
	public sealed class TableProviderWebPart : WebPart, IWebPartTable
	{
		DataTable _table;

		public TableProviderWebPart()
		{
			_table = new DataTable();

			DataColumn col = new DataColumn();
			col.DataType = typeof(string);
			col.ColumnName = "Name";
			_table.Columns.Add(col);

			col = new DataColumn();
			col.DataType = typeof(string);
			col.ColumnName = "Address";
			_table.Columns.Add(col);

			col = new DataColumn();
			col.DataType = typeof(int);
			col.ColumnName = "ZIP Code";
			_table.Columns.Add(col);

			DataRow row = _table.NewRow();
			row["Name"] = "John Q. Public";
			row["Address"] = "123 Main Street";
			row["ZIP Code"] = 98000;
			_table.Rows.Add(row);
		}

		public PropertyDescriptorCollection Schema
		{
			get
			{
				return TypeDescriptor.GetProperties(_table.DefaultView[0]);
			}
		}

		public void GetTableData(TableCallback callback)
		{
				callback(_table.Rows);
		}

		public bool ConnectionPointEnabled
		{
			get
			{
				object o = ViewState["ConnectionPointEnabled"];
				return (o != null) ? (bool)o : true;
			}
			set
			{
				ViewState["ConnectionPointEnabled"] = value;
			}
		}

		[ConnectionProvider("Table", typeof(TableProviderConnectionPoint), 
      AllowsMultipleConnections = true)]
		public IWebPartTable GetConnectionInterface()
		{
			return new TableProviderWebPart();
		}

		public class TableProviderConnectionPoint : ProviderConnectionPoint
		{
			public TableProviderConnectionPoint(MethodInfo callbackMethod, 
        Type interfaceType, Type controlType, string name, string id, 
        bool allowsMultipleConnections) 
        : base(callbackMethod, interfaceType, controlType, name, id, 
          allowsMultipleConnections)
			{
			}

			public override bool GetEnabled(Control control)
			{
				return ((TableProviderWebPart)control).ConnectionPointEnabled;
			}

		}

	}


  // This code sample creates a Web Parts control that acts as a consumer  
  // of information provided by the TableProvider.ascx control.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  public class TableConsumer : WebPart
  {
    private IWebPartTable _provider;
    private ICollection _tableData;

    private void GetTableData(object tableData)
    {
      _tableData = (ICollection)tableData;
    }

    protected override void OnPreRender(EventArgs e)
    {
      if (_provider != null)
      {
        _provider.GetTableData(new TableCallback(GetTableData));
      }
    }

    protected override void RenderContents(HtmlTextWriter writer)
    {
      if (_provider != null)
      {
        PropertyDescriptorCollection props = _provider.Schema;
        int count = 0;
        if (props != null && props.Count > 0 && _tableData != null)
        {
          foreach (PropertyDescriptor prop in props)
          {
            foreach (DataRow o in _tableData)
            {
              writer.Write(prop.DisplayName + ": " + o[count]);
            }
            writer.WriteBreak();
            writer.WriteLine();
            count = count + 1;
          }
        }
        else
        {
          writer.Write("No data");
        }
      }
      else
      {
        writer.Write("Not connected");
      }
    }

    [ConnectionConsumer("Table")]
    public void SetConnectionInterface(IWebPartTable provider)
    {
      _provider = provider;
    }

    public class TableConsumerConnectionPoint : ConsumerConnectionPoint
    {
      public TableConsumerConnectionPoint(MethodInfo callbackMethod,
        Type interfaceType, Type controlType, string name, string id,
        bool allowsMultipleConnections)
        : base(callbackMethod, interfaceType, controlType, name, id,
        allowsMultipleConnections)
      {
      }

    } // TableConsumerConnectionPoint

  } // TableConsumer

} // Samples.AspNet.CS.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="C#" %>
<%@ Register tagprefix="IRow" 
    Namespace="Samples.AspNet.CS.Controls" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>IRow Test Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <asp:webpartmanager ID="WebPartManager1" runat="server">
        <staticconnections>
          <asp:webpartconnection ID="wp1" ProviderID="provider1" 
            ConsumerID="consumer1">
          </asp:webpartconnection>
        </staticconnections>
      </asp:webpartmanager>

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

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

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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