Self-Join Using LINQ

Introduction

This article demonstrates an interesting and very useful concept in LINQ.

Question: What is self-join using LINQ?

In simple terms "It enables selection of data by performing a self-join on a table using LINQ query".

Step 1: Create a new web application

Output1.jpg

Step 2: Add a new Entity Framework

Output2.jpg

Output3.png



Step 3: The complete code of WebForm1.aspx is as in the following:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="SelfJoin_LINQ.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="Self Join with LINQ" 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"

                            AutoGenerateColumns="True">

                            <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 4: 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 SelfJoin_LINQ

{

    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 = from r in objEntities.tblEmployee join q in objEntities.tblEmployee on r.Id equals q.EmpRoleId select new

            {

                Id = r.FirstName + " " + r.LastName, RoleEmployees = q.FirstName + " " + q.LastName };

            GridView1.DataSource = query;

            GridView1.DataBind();

        }

        #region Instance MembersCompanyEntities objEntities = new CompanyEntities();

        #endregion

    }

}

Step 5: The output of the application is as in the following:

Output4.png

Step 6: The selected data output of the application is as in the following:

Output5.png

I hope this article was useful for you.


Similar Articles
MVC Corporation
MVC Corporation is consulting and IT services based company.