TableCallback Delegado

Definición

Espacio de nombres:

System.Web.UI.WebControls.WebParts

Ensamblado:

System.Web.dll

Hace referencia al método que se va a llamar cuando se recuperen los datos de la tabla de un proveedor.

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)

Parámetros

tableData

ICollection

Datos que se recuperan del proveedor.

Ejemplos

El ejemplo de código siguiente contiene un control elementos web denominado TableProviderWebPart que actúa como proveedor de datos en forma de tabla. El control incluye una implementación del GetTableData método , que recibe un parámetro de tipo TableCallback. Este método llama al método representado por el TableCallback delegado que pasa los datos de la tabla.

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

En el OnPreRender método , el consumidor llama GetTableData a en TableProviderWebPart y pasa su GetTableData método como delegado para llamar a con los datos de la tabla, como se muestra en el ejemplo de código siguiente.

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

Los dos controles y la conexión se incluyen en una página web, como se muestra en el ejemplo siguiente.

<%@ 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>

Comentarios

Cuando un control elementos web implementa la IWebPartTable interfaz y actúa como proveedor en una conexión elementos web, el consumidor o transformador debe recuperar y procesar los datos de la tabla del proveedor. El TableCallback delegado representa el método al que se va a llamar para procesar los datos del proveedor.

El GetTableData método contiene un TableCallback parámetro delegado.

Métodos de extensión

GetMethodInfo(Delegate)

Obtiene un objeto que representa el método representado por el delegado especificado.