IWebPartField.GetFieldValue Method (FieldCallback)
.NET Framework (current version)
Returns the value of the field that is being used by the interface as the basis of a connection between two WebPart controls.
Assembly: System.Web (in System.Web.dll)
Parameters
- callback
-
Type:
System.Web.UI.WebControls.WebParts.FieldCallback
A FieldCallback delegate that contains the address of a method that receives the data.
Use this method to retrieve the data field values passed by the interface.
The following code example shows the implementation and use of the GetFieldValue method. The complete example is shown in the class overview for the IWebPartField interface. The provider control implements the GetFieldValue method, returning the value of a particular field in the data table. The consumer control calls the GetFieldValue method in its OnPreRender method, so that the value of the data can be written to the page.
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 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 '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 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 'FieldConsumerWebPart 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 'FieldConsumerConnectionPoint End Namespace ' Samples.AspNet.VB.Controls
.NET Framework
Available since 2.0
Available since 2.0
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