CustomExpression Class

Definition

public ref class CustomExpression : System::Web::UI::WebControls::Expressions::ParameterDataSourceExpression

public class CustomExpression : System.Web.UI.WebControls.Expressions.ParameterDataSourceExpression

type CustomExpression = class
    inherit ParameterDataSourceExpression

Public Class CustomExpression
Inherits ParameterDataSourceExpression

Inheritance

Object

DataSourceExpression

ParameterDataSourceExpression

CustomExpression

Examples

The following example shows how to create a CustomExpression object that is used by the QueryExtender control. The custom expression calls the FilterProducts method, which contains a custom LINQ expression. The result of the filtering operation is displayed in a GridView control.

The following example shows an event handler that contains a custom LINQ query. The expression filters the Product table in the AdventureWorks database and displays products that have a list price greater than or equal to $3,500.00.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.Expressions;
using System.Linq;

public partial class _Default : System.Web.UI.Page 
{
    protected void FilterProducts(object sender, CustomExpressionEventArgs e)
    {
        e.Query = from p in e.Query.Cast<Product>()
                  where p.ListPrice >= 3500
                  select p;
    }
}

Imports System.Collections.Generic
Imports System.Linq
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.Expressions
Imports System.Data.Linq

Partial Class CustomVB
    Inherits System.Web.UI.Page

    Protected Sub FilterProducts(ByVal sender As Object, ByVal e As CustomExpressionEventArgs)
        e.Query = From p In e.Query.Cast(Of Product)() _
            Where p.ListPrice >= 3500 _
            Select p
    End Sub

Remarks

The CustomExpression class is used with the QueryExtender control. The QueryExtender control supports a variety of options that you can use to filter data. The QueryExtender control supports filters that let you search strings, search values between a specified range, compare a property value in a table to a specified value, and sort data. These options are provided as LINQ expressions in the QueryExtender control. You can use these filter expressions or you can provide a custom expression that you can use in the QueryExtender control. The CustomExpression class enables you to specify a custom expression in your application and call it in an event handler.

Constructors

Properties

Methods

Events

Explicit Interface Implementations

Applies to

See also

• QueryExtender Web Server Control Overview