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ObjectDataSourceFilteringEventHandler Delegate

Note: This delegate is new in the .NET Framework version 2.0.

Represents the method that will handle the Filtering event of the ObjectDataSource control.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

'Declaration
Public Delegate Sub ObjectDataSourceFilteringEventHandler ( _
	sender As Object, _
	e As ObjectDataSourceFilteringEventArgs _
)
'Usage
Dim instance As New ObjectDataSourceFilteringEventHandler(AddressOf HandlerMethod)
/** @delegate */
public delegate void ObjectDataSourceFilteringEventHandler (
	Object sender, 
	ObjectDataSourceFilteringEventArgs e
)
JScript supports the use of delegates, but not the declaration of new ones.

Parameters

sender

The source of the event, the ObjectDataSource.

e

An ObjectDataSourceFilteringEventArgs that contains the event data.

When you create an ObjectDataSourceFilteringEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Consuming Events.

This section contains two code examples. The first code example demonstrates how to display filtered data by using an ObjectDataSource control to retrieve data from a middle-tier business object, and then using a GridView control to display the results. The second code example provides an example of a middle-tier business object that is used by the first code example.

The following code example demonstrates how to display filtered data by using an ObjectDataSource control to retrieve data from a middle-tier business object, and then using a GridView control to display the results. The ObjectDataSource control can filter data only when the method that retrieves the data retrieves it as a DataSet or DataTable object. For this reason, the SelectMethod property identifies a business object method that retrieves data as a DataSet or DataTable object.

The code example consists of a TextBox control, a GridView control, the ObjectDataSource control, and a Submit button. By default, the TextBox control is populated with the name of one of the employees at Northwind Traders. The GridView control displays information about the employee who is identified by the name in the TextBox. To retrieve data for another employee, in the TextBox control, type the full name of the employee, and then click the Submit button.

The FilterExpression property specifies an expression that is used to filter the data that is retrieved by the method that is specified by the SelectMethod property. It uses parameter placeholders that are evaluated to the parameters that are contained in the FilterParameters collection. In this example, the parameter placeholder is enclosed by single quotation marks (') because the type of the parameter is a string type that might contain spaces. If the type of the parameter is numeric or date, quotation marks are not required. The FilterParameters collection contains one parameter, a FormParameter object that is bound to the TextBox control.

If no name is specified in the TextBox control, a new parameter is added to the ParameterValues collection so that the search is successful.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<script runat="server">

    Protected Sub ObjectDataSource1_Filtering(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ObjectDataSourceFilteringEventArgs)
        If Textbox1.Text = "" Then
            e.ParameterValues.Clear()
            e.ParameterValues.Add("FullName", "Nancy Davolio")
        End If
    End Sub
</script>

<html>
  <head>
    <title>ObjectDataSource - VB Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <p>Show all users with the following name.</p>

        <asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1"
          autogeneratecolumns="False">
          <columns>
            <asp:boundfield headertext="ID" datafield="EmpID" />
            <asp:boundfield headertext="Name" datafield="FullName" />
            <asp:boundfield headertext="Street Address" datafield="Address" />
          </columns>
        </asp:gridview>

        <!-- Security Note: The ObjectDataSource uses a FormParameter,
             Security Note: which does not perform validation of input from the client. -->

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          selectmethod="GetAllEmployeesAsDataSet"
          typename="Samples.AspNet.VB.EmployeeLogic"
          filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
            <filterparameters>
              <asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
            </filterparameters>
        </asp:objectdatasource>

        <p><asp:button id="Button1" runat="server" text="Search" /></p>

    </form>
  </body>
</html>

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL" Assembly="Samples.AspNet.JSL" %>
<%@ Page language="VJ#" %>
<script runat="server">

    protected void ObjectDataSource1_Filtering(Object sender, ObjectDataSourceFilteringEventArgs e)
    {
        if (Textbox1.get_Text() == "")
        {
            e.get_ParameterValues().Clear();
            e.get_ParameterValues().Add("FullName", "Nancy Davolio");
        }
    }
</script>

<html>
  <head>
    <title>ObjectDataSource - VJ# Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <p>Show all users with the following name.</p>

        <asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1"
          autogeneratecolumns="False">
          <columns>
            <asp:boundfield headertext="ID" datafield="EmpID" />
            <asp:boundfield headertext="Name" datafield="FullName" />
            <asp:boundfield headertext="Street Address" datafield="Address" />
          </columns>
        </asp:gridview>

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          selectmethod="GetAllEmployeesAsDataSet"
          typename="Samples.AspNet.JSL.EmployeeLogic"
          filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
            <filterparameters>
              <asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
            </filterparameters>
        </asp:objectdatasource>

        <p><asp:button id="Button1" runat="server" text="Search" /></p>

    </form>
  </body>
</html>

The following code example provides an example of a middle-tier business object that the preceding code example uses. The code example consists of two basic classes: EmployeeLogic and NorthwindEmployee. The EmployeeLogic class encapsulates business logic and the NorthwindEmployee class is a model class that contains only the basic functionality that is required to load and persist data from the data tier. For simplicity, the EmployeeLogic class creates a static set of data, rather than retrieving the data from a data tier. For a complete working example, you must compile and use these classes with the Web Forms code examples that are provided.

Imports System
Imports System.Collections
Imports System.Data
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB
'
' EmployeeLogic is a stateless business object that encapsulates 
' the operations you can perform on a NorthwindEmployee object.
'
Public Class EmployeeLogic
   
   ' Returns a collection of NorthwindEmployee objects.
   Public Shared Function GetAllEmployees() As ICollection
      Dim data As New ArrayList()
      
      data.Add(New NorthwindEmployee(1, "Nancy", "Davolio", "507 - 20th Ave. E. Apt. 2A"))
      data.Add(New NorthwindEmployee(2, "Andrew", "Fuller", "908 W. Capital Way"))
      data.Add(New NorthwindEmployee(3, "Janet", "Leverling", "722 Moss Bay Blvd."))
      data.Add(New NorthwindEmployee(4, "Margaret", "Peacock", "4110 Old Redmond Rd."))
      data.Add(New NorthwindEmployee(5, "Steven", "Buchanan", "14 Garrett Hill"))
      data.Add(New NorthwindEmployee(6, "Michael", "Suyama", "Coventry House Miner Rd."))
      data.Add(New NorthwindEmployee(7, "Robert", "King", "Edgeham Hollow Winchester Way"))
      
      Return data
   End Function 'GetAllEmployees
   
   
   Public Shared Function GetEmployee(anID As Object) As NorthwindEmployee
      Dim data As ArrayList = CType(GetAllEmployees(), ArrayList)
      Dim empID As Integer = Int32.Parse(anID.ToString())
      Return CType(data(empID),NorthwindEmployee)   
   End Function 'GetEmployee
   
   
   ' To support basic filtering, the employees cannot
   ' be returned as an array of objects, rather as a 
   ' DataSet of the raw data values. 
   Public Shared Function GetAllEmployeesAsDataSet() As DataSet
      Dim employees As ICollection = GetAllEmployees()
      
      Dim ds As New DataSet("Table")
      
      ' Create the schema of the DataTable.
      Dim dt As New DataTable()
      Dim dc As DataColumn
      dc = New DataColumn("EmpID", GetType(Integer))
      dt.Columns.Add(dc)
      dc = New DataColumn("FullName", GetType(String))
      dt.Columns.Add(dc)
      dc = New DataColumn("Address", GetType(String))
      dt.Columns.Add(dc)
      
      ' Add rows to the DataTable.
      Dim row As DataRow
      Dim ne As NorthwindEmployee
      For Each ne In employees         
         row = dt.NewRow()
         row("EmpID") = ne.EmpID
         row("FullName") = ne.FullName
         row("Address") = ne.Address
         dt.Rows.Add(row)
      Next
      ' Add the complete DataTable to the DataSet.
      ds.Tables.Add(dt)
      
      Return ds
   End Function 'GetAllEmployeesAsDataSet
      
End Class 'EmployeeLogic 


Public Class NorthwindEmployee
   
   Public Sub New(anID As Integer, aFirstName As String, aLastName As String, anAddress As String)
      ID = anID
      Me.aFirstName = aFirstName
      Me.aLastName = aLastName
      Me.aAddress = anAddress
   End Sub 'New
   
   Private ID As Object   
   Public ReadOnly Property EmpID() As String
      Get
         Return ID.ToString()
      End Get
   End Property 

   Private aLastName As String   
   Public Property LastName() As String
      Get
         Return aLastName
      End Get
      Set
         aLastName = value
      End Set
   End Property 

   Private aFirstName As String   
   Public Property FirstName() As String
      Get
         Return aFirstName
      End Get
      Set
         aFirstName = value
      End Set
   End Property 
   
   Public ReadOnly Property FullName() As String
      Get
         Return FirstName & " " & LastName
      End Get
   End Property 
  
   Private aAddress As String  
   Public Property Address() As String
      Get
         Return aAddress
      End Get
      Set
         aAddress = value
      End Set
   End Property 
   
End Class 'NorthwindEmployee
End Namespace

package Samples.AspNet.JSL ; 
import System .* ;
import System.Collections .* ;
import System.Data .* ;
import System.Web.UI.WebControls .* ;
//
// EmployeeLogic is a stateless business object that encapsulates 
// the operations you can perform on a NorthwindEmployee object.
//
public class EmployeeLogic
{
    // Returns a collection of NorthwindEmployee objects.
    public static ICollection GetAllEmployees()
    {
        ArrayList data = new ArrayList();

        data.Add(new NorthwindEmployee(1, "Nancy", "Davolio", 
            "507 - 20th Ave. E. Apt. 2A"));
        data.Add(new NorthwindEmployee(2, "Andrew", "Fuller", 
            "908 W. Capital Way"));
        data.Add(new NorthwindEmployee(3, "Janet", "Leverling", 
            "722 Moss Bay Blvd."));
        data.Add(new NorthwindEmployee(4, "Margaret", "Peacock", 
            "4110 Old Redmond Rd."));
        data.Add(new NorthwindEmployee(5, "Steven", "Buchanan", 
            "14 Garrett Hill"));
        data.Add(new NorthwindEmployee(6, "Michael", "Suyama", 
            "Coventry House Miner Rd."));
        data.Add(new NorthwindEmployee(7, "Robert", "King", 
            "Edgeham Hollow Winchester Way"));
        return data;
    } //GetAllEmployees


    public static NorthwindEmployee GetEmployee(Object anID)
    {
        ArrayList data = (ArrayList)GetAllEmployees();
        int empID = Int32.Parse(String.valueOf(anID));

        return (NorthwindEmployee)data.get_Item(empID);
    } //GetEmployee


    // 
    // To support basic filtering, the employees cannot
    // be returned as an array of objects, rather as a 
    // DataSet of the raw data values. 
    public static DataSet GetAllEmployeesAsDataSet()
    {
        ICollection employees = GetAllEmployees();
        DataSet ds = new DataSet("Table");

        // Create the schema of the DataTable.
        DataTable dt = new DataTable();
        DataColumn dc;

        dc = new DataColumn("EmpID", int.class.ToType());
        dt.get_Columns().Add(dc);
        dc = new DataColumn("FullName", String.class.ToType());
        dt.get_Columns().Add(dc);
        dc = new DataColumn("Address", String.class.ToType());
        dt.get_Columns().Add(dc);

        // Add rows to the DataTable.
        DataRow row;

		IEnumerator iterator = employees.GetEnumerator();
        for (int iCtr = 0; iCtr < employees.get_Count(); iCtr++) {
			iterator.MoveNext();
            NorthwindEmployee ne = 
                (NorthwindEmployee)iterator.get_Current();

            row = dt.NewRow();
            row.set_Item("EmpID", ne.get_EmpID());
            row.set_Item("FullName", ne.get_FullName());
            row.set_Item("Address", ne.get_Address());
            dt.get_Rows().Add(row);
        }

        // Add the complete DataTable to the DataSet.
        ds.get_Tables().Add(dt);
        return ds;
    } //GetAllEmployeesAsDataSet
} //EmployeeLogic



public class NorthwindEmployee
{
    public NorthwindEmployee(int anID, String aFirstName, String aLastName, 
        String anAddress)
    {
        ID = new Integer(anID);
        firstName = aFirstName;
        lastName = aLastName;
        address = anAddress;
    } //NorthwindEmployee


    private Object ID;


    /** @property */
    public String get_EmpID()
    {
        return ID.toString();
    } //get_EmpID


    private String lastName;


    /** @property */
    public String get_LastName()
    {
        return lastName;
    } //get_LastName


    /** @property */
    public void set_LastName(String value)
    {
        lastName = value;
    } //set_LastName


    private String firstName;


    /** @property */
    public String get_FirstName()
    {
        return firstName;
    } //get_FirstName


    /** @property */
    public void set_FirstName(String value)
    {
        firstName = value;
    } //set_FirstName


    /** @property */
    public String get_FullName()
    {
        return firstName + " " + lastName;
    } //get_FullName


    private String address;


    /** @property */
    public String get_Address()
    {
        return address;
    } //get_Address


    /** @property */
    public void set_Address(String value)
    {
        address = value;
    } //set_Address
} //NorthwindEmployee

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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