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

Vijay Prativadi
13y
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Article

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: