IWebPartTable.Schema Property
Gets the schema information for a data table that is used to share data between two WebPart controls.
Assembly: System.Web (in System.Web.dll)
Property Value
Type: System.ComponentModel.PropertyDescriptorCollectionA PropertyDescriptorCollection describing the data.
This property provides property information on the data in an IWebPartTable instance. There is an implicit contract between the schema referenced by the Schema property and the data in the table. The contract is that for each PropertyDescriptor object in the Schema property, you can call GetValue on an element of the table data to get the value in a column or a row of the table.
The following code example shows the implementation and use of the Schema property. The complete example is shown in the class overview for the IWebPartTable interface. The provider control implements the Schema property. Then the consumer control, in its RenderContents method, queries the Schema property to retrieve information about the table as it writes the table data 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 table data. <AspNetHostingPermission(SecurityAction.Demand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ <AspNetHostingPermission(SecurityAction.InheritanceDemand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ 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 Public ReadOnly Property Schema() As _ ComponentModel.PropertyDescriptorCollection Implements IWebPartTable.Schema Get Return TypeDescriptor.GetProperties(_table.DefaultView(0)) End Get End Property Public Sub GetTableData(ByVal callback As TableCallback) _ Implements IWebPartTable.GetTableData callback(_table.Rows) 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 <ConnectionProvider("Table", GetType(TableProviderConnectionPoint), _ AllowsMultipleConnections:=True)> _ Public Function GetConnectionInterface() As IWebPartTable Return New TableProviderWebPart() End Function End Class 'TableProviderWebPart ' The connection point for the provider control. <AspNetHostingPermission(SecurityAction.Demand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ <AspNetHostingPermission(SecurityAction.InheritanceDemand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ Public Class TableProviderConnectionPoint Inherits ProviderConnectionPoint 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, TableProviderWebPart).ConnectionPointEnabled End Function End Class ' 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 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 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 Dim prop As PropertyDescriptor For Each prop In props Dim o As DataRow For Each o In _tableData writer.Write(prop.DisplayName & ": " & o(count)) Next o writer.WriteBreak() writer.WriteLine() count = count + 1 Next prop 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 End Class 'TableConsumer ' The connection point for the consumer control. <AspNetHostingPermission(SecurityAction.Demand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ <AspNetHostingPermission(SecurityAction.InheritanceDemand, _ Level:=AspNetHostingPermissionLevel.Minimal)> _ Public 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 'TableConsumerConnectionPoint End Namespace ' Samples.AspNet.CS.Controls
Available since 2.0