Correlated Query Operation With Lambda Operator in C#

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

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

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

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">

.grid

{

margin-top: 50px;

}

</style>

</head>

<body>

<div>

<table>

<tr>

<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>

<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>

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

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

</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:

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