Select Data Using Complied Query

Introduction

Today, in this article let's play around with an interesting and very useful concept in Entity Framework.

What is a compiled query?

In simple terms "A query that is compiled once then executed several times".

Step 1. Create a new web application.

Step 2. Add a new Entity Data Model Framework.

Step 3. The complete code of WebForm1.aspx looks like this.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="CompliedQuerySelectData.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>
                <table>
                    <tr>
                        <td colspan="2" align="center">
                            <asp:Label ID="Label1" runat="server" Text="Select Data - Complied Query" Font-Bold="true" Font-Size="Large" Font-Names="Verdana" ForeColor="Maroon"></asp:Label>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <asp:Label ID="Label2" runat="server" Text="Please Enter FirstName" Font-Names="Verdana"></asp:Label>
                        </td>
                        <td>
                            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                        </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>
                    <tr>
                        <td colspan="2" align="center">
                            <asp:Label ID="Label3" runat="server" Font-Names="Verdana" Font-Bold="true"></asp:Label>
                        </td>
                    </tr>
                </table>
            </center>
        </div>
    </form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.Objects;

namespace CompliedQuerySelectData
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        private static readonly Func<CompanyEntities, string, IQueryable<tblEmployee>> compileQuery = CompiledQuery.Compile<CompanyEntities, string, IQueryable<tblEmployee>>((objEntities, firstName) => from c in objEntities.tblEmployees where c.FirstName == firstName select c);

        protected void Button1_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(TextBox1.Text))
            {
                Label3.Text = "Please Enter Some Values";
                Label3.ForeColor = System.Drawing.Color.Red;
            }
            else
            {
                GridView1.DataSource = getData(TextBox1.Text);
                GridView1.DataBind();
                TextBox1.Text = string.Empty;
            }
        }

        public object getData(string firstName)
        {
            return compileQuery(objEntities, firstName);
        }

        #region Instance Members
        CompanyEntities objEntities = new CompanyEntities();
        #endregion
    }
}