IWebPartField.Schema Property
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Gets the schema information for a data field that is used to share data between two WebPart controls.
public:
property System::ComponentModel::PropertyDescriptor ^ Schema { System::ComponentModel::PropertyDescriptor ^ get(); };public System.ComponentModel.PropertyDescriptor Schema { get; }member this.Schema : System.ComponentModel.PropertyDescriptorPublic ReadOnly Property Schema As PropertyDescriptorProperty Value
A PropertyDescriptor that describes the schema information for the data field.
Examples
The following code example shows the implementation and use of the Schema property. The complete example is shown in the class overview for the IWebPartField interface. The provider control implements the Schema property. Then, in its GetFieldValue method, it uses the property to retrieve the field value.
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
Remarks
This property provides property information for the data passed by the interface. Transformer and consumer controls can query this property to get information about the type, contents, and other details of the field contained in the IWebPartField interface instance sent by a provider.
