IWebPartRow.Schema Property

Definition

Namespace:

System.Web.UI.WebControls.WebParts

Assembly:

System.Web.dll

Gets the schema information for a data row that is used to share data between two WebPart controls.

public:
 property System::ComponentModel::PropertyDescriptorCollection ^ Schema { System::ComponentModel::PropertyDescriptorCollection ^ get(); };

public System.ComponentModel.PropertyDescriptorCollection Schema { get; }

member this.Schema : System.ComponentModel.PropertyDescriptorCollection

Public ReadOnly Property Schema As PropertyDescriptorCollection

Property Value

PropertyDescriptorCollection

A PropertyDescriptorCollection describing the data.

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 IWebPartRow 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 row as it writes the row data to the page.

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 row data.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  public sealed class RowProviderWebPart : WebPart, IWebPartRow 
    {
    private DataTable _table;
    
    public RowProviderWebPart() 
        {
      _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("Row")]
    public IWebPartRow GetConnectionInterface()
        {
      return new RowProviderWebPart();
    }

    public PropertyDescriptorCollection Schema 
        {
      get 
      {
        return TypeDescriptor.GetProperties(_table.DefaultView[0]);
            }
    }

        public void GetRowData(RowCallback callback)
        {
            callback(_table.Rows);
        }
  } // RowProviderWebPart

  // This sample code creates a Web Parts control that acts as a consumer 
  // of row data.
  [AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal)]
  [AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal)]  
  public sealed class RowConsumerWebPart : WebPart 
  {
    private IWebPartRow _provider;
        private ICollection _tableData;
    
        private void GetRowData(object rowData)
        {
            _tableData = (ICollection)rowData;
        }

        protected override void OnPreRender(EventArgs e)
        {
            if (_provider != null)
            {
                _provider.GetRowData(new RowCallback(GetRowData));
            }
        }

    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("Row")]
    public void SetConnectionInterface(IWebPartRow provider) 
        {
      _provider = provider;
    }
  } // RowConsumerWebPart
} // 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 row data.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public NotInheritable Class RowProviderWebPart
    Inherits WebPart
    Implements IWebPartRow
    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("Row")> _
    Public Function GetConnectionInterface() As IWebPartRow
      Return New RowProviderWebPart()

    End Function 'GetConnectionInterface


    Public ReadOnly Property Schema() As _
      ComponentModel.PropertyDescriptorCollection Implements IWebPartRow.Schema

      Get
        Return TypeDescriptor.GetProperties(_table.DefaultView(0))
      End Get

    End Property


    Public Sub GetRowData(ByVal callback As RowCallback) _
      Implements IWebPartRow.GetRowData
      callback(_table.Rows)

    End Sub

  End Class


  ' This sample code creates a Web Parts control that acts as a consumer 
  ' of row data.
  <AspNetHostingPermission(SecurityAction.Demand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  <AspNetHostingPermission(SecurityAction.InheritanceDemand, _
    Level:=AspNetHostingPermissionLevel.Minimal)> _
  Public NotInheritable Class RowConsumerWebPart
    Inherits WebPart
    Private _provider As IWebPartRow
    Private _tableData As ICollection


    Private Sub GetRowData(ByVal rowData As Object)
      _tableData = CType(rowData, ICollection)

    End Sub


    Protected Overrides Sub OnPreRender(ByVal e As EventArgs)

      If Not (_provider Is Nothing) Then
        _provider.GetRowData(New RowCallback(AddressOf GetRowData))
      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))
              writer.WriteBreak()
              writer.WriteLine()
              count = count + 1
            Next o
          Next prop
        Else
          writer.Write("No data")
        End If
      Else
        writer.Write("Not connected")
      End If

    End Sub


    <ConnectionConsumer("Row")> _
    Public Sub SetConnectionInterface(ByVal provider As IWebPartRow)
      _provider = provider

    End Sub

  End Class

End Namespace  ' Samples.AspNet.VB.Controls

Remarks

This property provides property information for the data. Using the IWebPartRow interface in a connection, you get a PropertyDescriptorCollection object, which is referenced by the Schema property. The contract specifies that calling Schema[n].GetValue(RowData) returns the value of the nth column in the row. You need to use the Schema property to get the values in the row.

See also

• PropertyDescriptorCollection