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

Introduction

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 with lambda?

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

Step 1: Create a new "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" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

</head>

<body>

<div>

<table>

<tr>

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

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>

<br />

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

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

GridLines="None" AutoGenerateColumns="False">

</PagerStyle>

<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" />

</Columns>

</asp:GridView>

</td>

</tr>

</table>

</div>

</center>

</form>

</body>

</html>

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 = objEntities.Employee.Join

(

objEntities.Position, r => r.EmpId, p => p.EmpId, (r, p) => new

{

r.FirstName,

r.LastName,

p.Position1,

p.PosId

}

)

.Join(objEntities.Salary, a => a.PosId, b => b.PosId, (a, b) => new

{

a.FirstName,

a.LastName,

a.Position1,

b.Salary1

});

GridView1.DataSource = query;

GridView1.DataBind();

}

#region Instance MembersCompanyEntities objEntities = new CompanyEntities();

#endregion

}

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

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