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]()