ObjectDataSourceView.FilterParameters Property


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Gets a collection of parameters that are associated with any parameter placeholders that are in the FilterExpression string.

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

Public ReadOnly Property FilterParameters As ParameterCollection

Property Value

Type: System.Web.UI.WebControls.ParameterCollection

A ParameterCollection that contains a set of parameters associated with any parameter placeholders found in the FilterExpression property.

Exception Condition

The FilterExpression property was set and the Select method does not return a DataSet.

The ObjectDataSource control supports filtering data only when the Select method returns a DataSet, DataTable, or DataView object.

The parameters in the FilterParameters collection are associated with any parameters that are specified in the FilterExpression property. The parameter placeholders that are specified in the FilterExpression property are matched to parameter objects in the FilterParameters collection when the method specified by the SelectMethod property is called.

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

The following code example demonstrates how to display filtered data using an ObjectDataSource control to retrieve data from a middle-tier business object and 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 object. For this reason, the SelectMethod property identifies a business object method that retrieves data as a DataSet.

The code example consists of a TextBox, a GridView control, the ObjectDataSource control, and a Submit button. By default, the TextBox is populated with the name of one of the Northwind Traders employees. The GridView displays information about the employee that is identified by the name in the TextBox. To retrieve data on another employee, in the TextBox, enter 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 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 bounded 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 a numeric or date type, bounding quotation marks are not required. The FilterParameters collection contains one parameter, a FormParameter that is bound to the TextBox control.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<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.Add("FullName", "Nancy Davolio")
        End If
    End Sub

<html xmlns="http://www.w3.org/1999/xhtml" >
    <title>ObjectDataSource - VB Example</title>
    <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:boundfield headertext="ID" datafield="EmpID" />
            <asp:boundfield headertext="Name" datafield="FullName" />
            <asp:boundfield headertext="Street Address" datafield="Address" />

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

          filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
              <asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />

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


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:

  • The EmployeeLogic class, which is a class that encapsulates business logic.

  • The NorthwindEmployee class, which 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. It is also helpful for this example, because the sample relies on you to provide the full name of a Northwind Traders employee to demonstrate filtering.

For a complete working example, you must compile and use these classes with the Web Forms page 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))
      dc = New DataColumn("FullName", GetType(String))
      dc = New DataColumn("Address", GetType(String))

      ' 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
      ' Add the complete DataTable to the DataSet.

      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
         Return ID.ToString()
      End Get
   End Property 

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

   Private aFirstName As String   
   Public Property FirstName() As String
         Return aFirstName
      End Get
         aFirstName = value
      End Set
   End Property 

   Public ReadOnly Property FullName() As String
         Return FirstName & " " & LastName
      End Get
   End Property 

   Private aAddress As String  
   Public Property Address() As String
         Return aAddress
      End Get
         aAddress = value
      End Set
   End Property 

End Class 'NorthwindEmployee
End Namespace

.NET Framework
Available since 2.0
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