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Correlated Query Operation With Lambda Operator in C#

Posted by Vijay Prativadi Articles | LINQ November 28, 2012
Today, in this article let's play around with one of the interesting and most useful concepts in C# with Lambda.
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Introduction

Today, in this article let's play around with one of the interesting and most useful concepts in C# with Lambda.

Question: What is correlated query operation with Lambda operator (=>) in C#?

In simple terms "It provides the ability to perform a correlated query operation with a Lambda operator in C#".

Step 1: Create a new WebForm project

New-project-in-asp.net.jpg

Step 2: The employee table output of the application looks like this:

Department-table-in-SQL-Server.jpg

Step 3: The department table output of the application looks like this:

Department-table-in-SQL-Server.jpg

Step 4: The complete code of WebForm1.aspx looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="Co_related_Operation_Lambda_App.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">

    <style type="text/css">

        .grid

        {

            margin-top: 50px;

        }

    </style>

    <title></title>

</head>

<body>

    <form id="form1" runat="server">

    <center>

        <div>

            <table>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Label ID="Label1" runat="server" Text="Correlated Queries using Lambda Operator (=>)"

                            Font-Bold="true" Font-Size="Large" Font-Names="Verdana" ForeColor="Maroon"></asp:Label>

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Button ID="Button1" runat="server" Text="Select Data" Font-Names="Verdana" Width="213px"

                            BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:GridView ID="GridView1" runat="server" CssClass="grid" BackColor="LightGoldenrodYellow"

                            BorderColor="Tan" BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None">

                            <AlternatingRowStyle BackColor="PaleGoldenrod" />

                            <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>

                    </td>

                </tr>

            </table>

        </div>

    </center>

    </form>

</body>

</html>


Step 5: The complete code of WebForm1.aspx.cs looks like this:
 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace Co_related_Operation_Lambda_App

{

    public partial class WebForm1 : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

        }

        protected void Button1_Click(object sender, EventArgs e)

        {

            var query = objEntities.Employee.Where(r => r.Location == objEntities.Department.Where(q => q.Location == r.Location).Select(q => q.Location).FirstOrDefault()).Select(r => new { FirstName = r.FirstName, LastName = r.LastName, Age = r.Age, Location = r.Location });

            GridView1.DataSource = query; GridView1.DataBind();

        }

        #region Instance

        MembersCompanyEntities objEntities = new CompanyEntities();

        #endregion

    }

}

Step 6: The output of the application looks like this:


App-output-in-asp.net.jpg

Step 7: The co-relation operation with Lambda output of the application looks like this:


corelated-queries-in-asp.net.jpg

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