ObjectDataSourceFilteringEventHandler Delegate
Represents the method that will handle the Filtering event of the ObjectDataSource control.
Assembly: System.Web (in System.Web.dll)
Public Delegate Sub ObjectDataSourceFilteringEventHandler ( sender As Object, e As ObjectDataSourceFilteringEventArgs )
Parameters
- sender
-
Type:
System.Object
The source of the event, the ObjectDataSource.
- e
-
Type:
System.Web.UI.WebControls.ObjectDataSourceFilteringEventArgs
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 NIB: 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" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <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 xmlns="http://www.w3.org/1999/xhtml" > <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>
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 'NewNew 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
Available since 2.0