TableCallback Delegate

Reference

Definition

Namespace:: System.Web.UI.WebControls.WebParts

Assembly:: System.Web.dll

Important

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References the method to call when retrieving table data from a provider.

public delegate void TableCallback(ICollection ^ tableData);

public delegate void TableCallback(ICollection tableData);

type TableCallback = delegate of ICollection -> unit

Public Delegate Sub TableCallback(tableData As ICollection)

Parameters

tableData: ICollection

The data to retrieve from the provider.

Examples

The following code example contains a Web Parts control named TableProviderWebPart that serves as a provider of data in the form of a table. The control includes an implementation of the GetTableData method, which receives a parameter of type TableCallback. This method calls the method represented by the TableCallback delegate passing the table data.

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Reflection;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
//This sample code creates a Web Parts control that acts as a provider of table data.
namespace Samples.AspNet.CS.Controls
{
    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")]
        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;
            }
        }
    }
}

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

'This sample code creates a Web Parts control that acts as a provider of table data.
Namespace Samples.AspNet.VB.Controls

    Public NotInheritable Class TableProviderWebPart
        Inherits WebPart
        Implements IWebPartTable

        Private _table As DataTable


        Public Sub New()
            _table = New DataTable()

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

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

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

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

        End Sub

        <ConnectionProvider("Table")> _
        Public Function GetConnectionInterface() As IWebPartTable
            Return New TableProviderWebPart()

        End Function 'GetConnectionInterface

        Public ReadOnly Property Schema() As PropertyDescriptorCollection _
            Implements IWebPartTable.Schema
            Get
                Return TypeDescriptor.GetProperties(_table.DefaultView(0))
            End Get
        End Property

        Public Property ConnectionPointEnabled() As Boolean
            Get
                Dim o As Object
                o = ViewState("ConnectionPointEnabled")
                If Not (o Is Nothing) Then
                    Return CBool(o)
                Else
                    Return True
                End If

            End Get
            Set(ByVal value As Boolean)
                ViewState("ConnectionPointEnabled") = value
            End Set
        End Property

        Public Sub GetTableData(ByVal callback As TableCallback) _
            Implements IWebPartTable.GetTableData
            callback(_table.Rows)

        End Sub
    End Class

End Namespace

In the OnPreRender method, the consumer calls GetTableData in TableProviderWebPart and passes its GetTableData method as the delegate to call with the table data, as shown in the following code example.

namespace Samples.AspNet.CS.Controls
{
    using System;
    using System.ComponentModel;
    using System.Data;
    using System.Data.SqlClient;
    using System.Reflection;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Collections;

    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;
        }
    }
}

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

Namespace Samples.AspNet.VB.Controls

    Public Class TableConsumerWebPart
        Inherits WebPart

        Private _provider As IWebPartTable
        Private _tableData As ICollection

        Private Sub GetTableData(ByVal tableData As ICollection)
            _tableData = CType(tableData, ICollection)

        End Sub

        Protected Overrides Sub OnPreRender(ByVal e As EventArgs)
            If Not (_provider Is Nothing) Then
                _provider.GetTableData((New TableCallback(AddressOf GetTableData)))
            End If
            'MyBase.OnPreRender(e)

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

        End Sub

        <ConnectionConsumer("Table")> _
        Public Sub SetConnectionInterface(ByVal provider As IWebPartTable)
            _provider = provider

        End Sub

        Private Class TableConsumerConnectionPoint
            Inherits ConsumerConnectionPoint

            Public Sub New(ByVal callbackMethod As MethodInfo, _
              ByVal interfaceType As Type, ByVal controlType As Type, _
              ByVal name As String, ByVal id As String, _
              ByVal allowsMultipleConnections As Boolean)
                MyBase.New(callbackMethod, interfaceType, controlType, _
                  name, id, allowsMultipleConnections)

            End Sub
        End Class
    End Class

End Namespace

The two controls and the connection are included in a Web page, as shown in the following example.

<%@ page language="C#" %>
<%@ Register tagprefix="wp" 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">
<script runat="server">

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>ITable Test Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <!-- A static or dynamic connection is required to link two
             Web Parts controls. --->
        <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>
            <!-- The following two lines define the 
              two connected controls. --->
            <wp:TableProviderWebPart ID="provider1" runat="server" 
               title="Web Parts Table Provider Control" />
            <wp:TableConsumer ID="consumer1" runat="server" 
               title="Web Parts Table Consumer Control"/>
            </zoneTemplate>
        </asp:webpartzone>
    </div>
    </form>
</body>
</html>

<%@ Page Language="VB" %>
<%@ Register tagprefix="wp" Namespace="Samples.AspNet.VB.Controls"  %>

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

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>ITable Test Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <!-- A static or dynamic connection is required to 
             link two Web Parts controls. --->
        <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>
            <!-- The following two lines define the two 
                 connected controls. --->
            <wp:TableProviderWebPart ID="provider1" runat="server" 
               title="Web Parts Table Provider Control" />
            <wp:TableConsumerWebPart ID="consumer1" runat="server" 
               title="Web Parts Table Consumer Control"/>
            </zoneTemplate>
        </asp:webpartzone>
    </div>
    </form>
</body>
</html>

Remarks

When a Web Parts control implements the IWebPartTable interface and serves as a provider in a Web Parts connection, the consumer or transformer must retrieve and process the table data from the provider. The TableCallback delegate represents the method to call for processing the provider data.

The GetTableData method contains a TableCallback delegate parameter.

Extension Methods

GetMethodInfo(Delegate)

Gets an object that represents the method represented by the specified delegate.

Applies to

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