Select Data Using Complied Query

Vijay Prativadi
Feb 12, 2013
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Introduction

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

Question: 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: Addi 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">

</head>

<body>

<div>

<table>

<tr>

<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>

<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>

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

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

No Records Found!</EmptyDataTemplate>

</asp:GridView>

</td>

</tr>

<tr>

<asp:Label ID="Label3" runat="server" Font-Names="Verdana" Font-Bold="true"></asp:Label>

</td>

</tr>

</table>

</center>

</div>

</form>

</body>

</html>

Step 4: 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;

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.tblEmployeewhere c.FirstName == firstNameselect 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 MembersCompanyEntities objEntities = new CompanyEntities();

#endregion

}

}

Step 5: The output of the application looks like this:

Step 6: The selected data output of the application looks like this:

I hope this article was useful for you.