Introduction
This article demonstrates an interesting and very useful concept in ASP.NET.
Question: What is query extender?
In simple terms "It filters the data from a selected data source".
Step 1: Create a new web application
![Output1.jpg]()
Step 2: Adding a new LINQ-to-SQL
![Output2.jpg]()
Step 3: Add new data source to GridView
![Output3.png]()
![Output5.jpg]()
![Output6.png]()
![Output7.png]()
![Output8.png]()
Step 4: The complete code of WebForm1.aspx is as in the following:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="QueryExtenderApp.WebForm1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<center>
<div>
<table>
<tr>
<td colspan="3" align="center">
<asp:Label ID="Label2" runat="server" Text="Query Extender" Font-Bold="true" Font-Names="Verdana"
Font-Size="Large"></asp:Label>
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label1" runat="server" Font-Names="Verdana" Font-Bold="true" Text="Please Filter By FirstName"></asp:Label>
</td>
<td>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</td>
</tr>
</table>
</div>
<div>
<asp:GridView ID="GridView1" runat="server" BackColor="LightGoldenrodYellow" BorderColor="Tan"
BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None" AutoGenerateColumns="False"
DataKeyNames="EmpId" DataSourceID="LinqDataSource1">
<AlternatingRowStyle BackColor="PaleGoldenrod" />
<Columns>
<asp:BoundField DataField="EmpId" HeaderText="EmpId" InsertVisible="False" ReadOnly="True"
SortExpression="EmpId" />
<asp:BoundField DataField="FirstName" HeaderText="FirstName" SortExpression="FirstName" />
<asp:BoundField DataField="LastName" HeaderText="LastName" SortExpression="LastName" />
<asp:BoundField DataField="Age" HeaderText="Age" SortExpression="Age" />
</Columns>
<FooterStyle BackColor="Tan" />
<HeaderStyle BackColor="Tan" Font-Bold="True" />
<PagerStyle BackColor="PaleGoldenrod" ForeColor="DarkSlateBlue" HorizontalAlign="Center" />
<SelectedRowStyle BackColor="DarkSlateBlue" ForeColor="GhostWhite" />
<SortedAscendingCellStyle BackColor="#FAFAE7" />
<SortedAscendingHeaderStyle BackColor="#DAC09E" />
<SortedDescendingCellStyle BackColor="#E1DB9C" />
<SortedDescendingHeaderStyle BackColor="#C2A47B" />
</asp:GridView>
<asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="QueryExtenderApp.DataClasses1DataContext"
EntityTypeName="" TableName="Employees">
</asp:LinqDataSource>
<br />
<asp:QueryExtender ID="QueryExtender1" runat="server" TargetControlID="LinqDataSource1">
<asp:SearchExpression DataFields="FirstName" SearchType="StartsWith">
<asp:ControlParameter ControlID="TextBox1" />
</asp:SearchExpression>
</asp:QueryExtender>
</div>
</center>
</form>
</body>
</html>
Step 5: The complete code of WebForm1.aspx.cs is as in the following:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace QueryExtenderApp
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
}
Step 6: The output of the application is as in the following:
![Output9.png]()
Step 7: The selected output of the application is as in the following:
![Output10.png]()
I hope this article was useful for you.