Introduction

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

Question: What is union operation using Lambda?

In simple terms "It enables the performance of a union operation using a Lambda query based on the requested entities".

Step 1: Create a new web application

Output1.jpg

Step 2: Add a new ADO.NET Entity Framework model

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="UnionLambdaApp.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="Select Data with Lambda - UNION Operation"
 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 UnionLambdaApp

{

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.Customer.Select(r => r.FirstName).Union(objEntities.Employee.Select(q => q.FirstName));

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.