Select Data - Eager Loading

Vijay Prativadi
11y
2.9k
0
0

Article

Introduction

This working demonstrates an interesting and very useful concept in Entity Framework.

Question: What is eager loading?

In simple terms "when the loop is started, each of the objects that you have specified will be pulled from the database and built into a gigantic in-memory data structure. This will be a very expensive operation, pulling an enormous amount of data from your database. However, it will all happen in one database round trip, with a single SQL query execution".

Step 1: Create a new web application

Step 2: Adding a new Entity Data Model Framework

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

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="SelectDataEagerLoadingApp.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">
     <title></title>
</head>
<body>
     <form id="form1" runat="server">
         <div>
             <center>
                 <div>
                     <table>
                         <tr>
                             <td colspan="2" align="center">
                                 <asp:Label ID="Label1" runat="server" Text="Select Data - Eager Loading" 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">
                                     <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" />
                                     <EmptyDataTemplate>No Records Found!</EmptyDataTemplate>
                                 </asp:GridView>
                             </td>
                         </tr>
                     </table>
                 </div>
             </center>
         </div>
     </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 SelectDataEagerLoadingApp
{
     public partial class WebForm1 : System.Web.UI.Page
     {
         protected void Page_Load(object sender, EventArgs e) { }
         protected void Button1_Click(object sender, EventArgs e)
         {
             using (CompanyEntities objEntities = new CompanyEntities())
             {
                 objEntities.ContextOptions.LazyLoadingEnabled = false;
                 GridView1.DataSource = objEntities.tblEmployee.Take(15).ToList();
                 GridView1.DataBind();
             }
         }
     }
}

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

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

I hope this working was useful for you. I look forward for your comments and feedback. Thanks Vijay.

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