Let Keyword Using LINQ

Vijay Prativadi
11y
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Article

Introduction

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

Question: What is let keyword?

In simple terms "It is a variable used to store some value, that can be then used across the query to operate with the stored value".

Step 1: Create a new web application

Step 2: Add 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="LetKeywordusingLINQ.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 Let Keyword using LINQ" 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" />
                            </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 LetKeywordusingLINQ
{
    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.tblEmployeelet bonusSal = r.Salary + 1000where bonusSal > 5000select new
            { FirstName = r.FirstName, LastName = r.LastName, Age = r.Age };
            GridView1.DataSource = query;
            GridView1.DataBind();
        }
        #region Instance MembersCompanyEntities objEntities = new CompanyEntities();
        #endregion
    }
}

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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