Inner Join Using LINQ For Multiple Tables (3 Tables Now)



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


Question: What is inner join using LINQ for multiple tables?


In simple terms "It provides flexibility to pull out the matching result sets from 3 or more tables using a LINQ inner join.".


Step 1: Create a "ASP.NET Web Application", as in:



Step 2: The design of the Employee table looks like this:



Step 3: The design of the Position table looks like this:



Step 4: The design of the Salary table looks like this:



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


<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs"Inherits="LINQInnerJoinApp._Default" %>


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<html xmlns="">

<head id="Head1" runat="server">




   <form id="form1" runat="server">





                    <td colspan="2">

                        <asp:Label ID="Label1" runat="server" Text="INNER JOIN using LINQ for Multiple Tables (3 Tables)"

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




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

                        <br />

                        <asp:GridView ID="GridView1" runat="server" BackColor="LightGoldenrodYellow"BorderColor="Tan"

                            BorderWidth="1px" CellPadding="2" EnableModelValidation="True" ForeColor="Black"

                            GridLines="None" AutoGenerateColumns="False">

                            <AlternatingRowStyle BackColor="PaleGoldenrod"></AlternatingRowStyle>

                            <FooterStyle BackColor="Tan"></FooterStyle>

                            <HeaderStyle BackColor="Tan" Font-Bold="True"></HeaderStyle>

                            <PagerStyle HorizontalAlign="Center" BackColor="PaleGoldenrod"ForeColor="DarkSlateBlue">


                            <SelectedRowStyle BackColor="DarkSlateBlue" ForeColor="GhostWhite"></SelectedRowStyle>


                                <asp:BoundField DataField="FirstName" HeaderText="First Name" ReadOnly="true" />

                                <asp:BoundField DataField="LastName" HeaderText="Last Name" />

                                <asp:BoundField DataField="Position1" HeaderText="Position" />

                                <asp:BoundField DataField="Salary1" HeaderText="Salary" />












Step 6: 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 LINQInnerJoinApp


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


        protected void Page_Load(object sender, EventArgs e)



        protected void Button1_Click(object sender, EventArgs e)


            var query =from rin objEntities.Employeejoin p in objEntities.Position on r.EmpId equals p.EmpIdjoin qinobjEntities.Salary on p.PosId equals q.PosIdselect new{r.FirstName,r.LastName,p.Position1,q.Salary1};

            GridView1.DataSource = query;




        Instance MembersCompanyEntities objEntities =new CompanyEntities();





Step 7: The output of the application looks like this:



Step 8: The results retrieved output of the application looks like this:


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