IWebPartField.GetFieldValue(FieldCallback) 方法

定义

返回字段的值,该字段由接口用作两个 WebPart 控件之间的连接基础。

public:
 void GetFieldValue(System::Web::UI::WebControls::WebParts::FieldCallback ^ callback);
public void GetFieldValue (System.Web.UI.WebControls.WebParts.FieldCallback callback);
abstract member GetFieldValue : System.Web.UI.WebControls.WebParts.FieldCallback -> unit
Public Sub GetFieldValue (callback As FieldCallback)

参数

callback
FieldCallback

一个 FieldCallback 委托,包含接收数据的方法的地址。

示例

下面的代码示例演示 方法的 GetFieldValue 实现和使用。 接口的类概述 IWebPartField 中显示了完整的示例。 提供程序控件实现 GetFieldValue 方法,返回数据表中特定字段的值。 使用者控件在其 OnPreRender 方法中调用 GetFieldValue 方法,以便可以将数据的值写入页面。

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 field data.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  public sealed class FieldProviderWebPart : WebPart, IWebPartField
  {
    private DataTable _table;

    public FieldProviderWebPart() 
    {
        _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);
    }

      [ConnectionProvider("FieldProvider")]
      public IWebPartField GetConnectionInterface()
    {
        return new FieldProviderWebPart();
    }

    public PropertyDescriptor Schema 
    {
        get 
        {
            /* The two parameters are row and field. Zero is the first record. 
                0,2 returns the zip code field value.   */ 
            return TypeDescriptor.GetProperties(_table.DefaultView[0])[2];
        }
    }

      void IWebPartField.GetFieldValue(FieldCallback callback) 
    {
        callback(Schema.GetValue(_table.DefaultView[0]));
    }
  } // end FieldProviderWebPart

  // This sample code creates a Web Parts control that acts as a consumer 
  // of an IWebPartField interface.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  public class FieldConsumerWebPart : WebPart
  {

    private IWebPartField _provider;
    private object _fieldValue;

    private void GetFieldValue(object fieldValue)
    {
      _fieldValue = fieldValue;
    }

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

    protected override void OnPreRender(EventArgs e)
    {
      if (_provider != null)
      {
        _provider.GetFieldValue(new FieldCallback(GetFieldValue));
      }
      base.OnPreRender(e);
    }

    protected override void RenderContents(HtmlTextWriter writer)
    {

      if (_provider != null)
      {
        PropertyDescriptor prop = _provider.Schema;

        if (prop != null && _fieldValue != null)
        {
          writer.Write(prop.DisplayName + ": " + _fieldValue);
        }
        else
        {
          writer.Write("No data");
        }
      }
      else
      {
        writer.Write("Not connected");
      }
    }

    [ConnectionConsumer("FieldConsumer", "Connpoint1", 
      typeof(FieldConsumerConnectionPoint), AllowsMultipleConnections = true)]
    public void SetConnectionInterface(IWebPartField provider)
    {
      _provider = provider;
    }

    public class FieldConsumerConnectionPoint : ConsumerConnectionPoint
    {
      public FieldConsumerConnectionPoint(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 ((FieldConsumerWebPart)control).ConnectionPointEnabled;
      }
    } // end FieldConsumerConnectionPoint
  } // end FieldConsumerWebPart
} // end namespace Samples.AspNet.CS.Controls
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 field data.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public NotInheritable Class FieldProviderWebPart
    Inherits WebPart
    Implements IWebPartField
    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("FieldProvider")> _
    Public Function GetConnectionInterface() As IWebPartField
      Return New FieldProviderWebPart()

    End Function


    Public ReadOnly Property Schema() As ComponentModel.PropertyDescriptor _
      Implements IWebPartField.Schema
      Get
        ' The two parameters are row and field. Zero is the first record. 
        ' 0,2 returns the zip code field value.   
        Return TypeDescriptor.GetProperties(_table.DefaultView(0))(2)
      End Get
    End Property


    Sub GetFieldValue(ByVal callback As FieldCallback) _
      Implements IWebPartField.GetFieldValue

      callback(Schema.GetValue(_table.DefaultView(0)))

    End Sub

  End Class


  ' This sample code creates a Web Parts control that acts as a 
  ' consumer of an IWebPartField interface.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public Class FieldConsumerWebPart
    Inherits WebPart

    Private _provider As IWebPartField
    Private _fieldValue As Object


    Private Sub GetFieldValue(ByVal fieldValue As Object)
      _fieldValue = fieldValue

    End Sub


    Public Property ConnectionPointEnabled() As Boolean
      Get
        Dim o As Object = ViewState("ConnectionPointEnabled")
        Return IIf(Not (o Is Nothing), CBool(o), True)
      End Get
      Set(ByVal value As Boolean)
        ViewState("ConnectionPointEnabled") = value
      End Set
    End Property


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

    End Sub


    Protected Overrides Sub RenderContents(ByVal writer As _
      HtmlTextWriter)

      If Not (_provider Is Nothing) Then
        Dim prop As PropertyDescriptor = _provider.Schema

        If Not (prop Is Nothing) AndAlso Not (_fieldValue Is Nothing) Then
          writer.Write(prop.DisplayName & ": " & _fieldValue)
        Else
          writer.Write("No data")
        End If
      Else
        writer.Write("Not connected")
      End If

    End Sub

    <ConnectionConsumer("FieldConsumer", "Connpoint1", _
      GetType(FieldConsumerConnectionPoint), AllowsMultipleConnections:=True)> _
    Public Sub SetConnectionInterface(ByVal provider As IWebPartField)
      _provider = provider

    End Sub

  End Class

  Public Class FieldConsumerConnectionPoint
    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


    Public Overrides Function GetEnabled(ByVal control As Control) _
      As Boolean

      Return CType(control, FieldConsumerWebPart).ConnectionPointEnabled

    End Function

  End Class

End Namespace  ' Samples.AspNet.VB.Controls

注解

使用此方法检索接口传递的数据字段值。

适用于