Union Operation Using LINQ


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

Question: What is union operation using LINQ?

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

Step 1: Create a new web application


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



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

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="UnionLINQ.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">



            margin-top: 50px;






    <form id="form1" runat="server">





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

                        <asp:Label ID="Label1" runat="server" Text="Select Data with LINQ - UNION Operation"

                            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">

                        <asp:GridView ID="GridView1" runat="server" CssClass="grid" BackColor="LightGoldenrodYellow"

                            BorderColor="Tan" BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None"


                            <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" />










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 UnionLINQ


    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.Customerselect new


                FirstName = r.FirstName


            ).Union(from p in objEntities.Employeeselect new


                FirstName = p.FirstName



            GridView1.DataSource = query;GridView1.DataBind();


        #region Instance MembersCompanyEntities objEntities = new CompanyEntities();




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


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


I hope this article was useful for you.

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