Lambda Expressions and LINQ in ASP.NET Web Forms

Riya
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1. Introduction

C# has evolved to make developers’ lives easier — and Lambda Expressions and LINQ (Language Integrated Query) are two powerful tools that simplify how we write, read, and manage data.

In traditional ASP.NET Web Forms, you may have written lengthy code to:

Filter a list of data
Search records by condition
Sort or group collections

With LINQ and Lambda Expressions, all these tasks can be done in one line of code 🚀.

2. What Are Lambda Expressions?

A Lambda Expression is a short, inline way to write anonymous methods.

Syntax

(parameters) => expression_or_statement

Example

x => x * x

This means: “Take input x, and return x * x.”

3. What Is LINQ?

LINQ (Language Integrated Query) allows querying collections, arrays, or databases in C# directly — using SQL-like syntax.

Example

var result = from n in numbers
             where n > 50
             select n;

Or using Lambda

var result = numbers.Where(n => n > 50);

LINQ works with:

Arrays and Lists (System.Linq)
DataTables
Entity Framework (Database LINQ)
XML data

4. Real-Time Example in ASP.NET Web Forms

Let’s create a web page that displays a product list and allows users to search products by name or price range — all powered by LINQ and Lambda.

Step 1: Create ASPX Page – ProductList.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ProductList.aspx.cs" Inherits="ProductList" %>

<!DOCTYPE html>
<html>
<head>
    <title>LINQ and Lambda in ASP.NET WebForms</title>
</head>
<body>
    <form id="form1" runat="server">
        <div style="width:600px; margin:auto; text-align:center; font-family:Arial;">
            <h2> Product Search using LINQ & Lambda</h2>

            <asp:Label ID="lblSearch" runat="server" Text="Enter Product Name or Price Range:"></asp:Label><br />
            <asp:TextBox ID="txtSearch" runat="server" Width="250px"></asp:TextBox><br /><br />

            <asp:Button ID="btnSearch" runat="server" Text="Search" OnClick="btnSearch_Click" /><br /><br />

            <asp:GridView ID="gvProducts" runat="server" AutoGenerateColumns="true"
                BorderColor="#ccc" BorderStyle="Solid" BorderWidth="1px" />
        </div>
    </form>
</body>
</html>

Aspx

Step 2: Code Behind – ProductList.aspx.cs

using System;using System.Collections.Generic;using System.Linq;

public partial class ProductList : System.Web.UI.Page{
    // Sample Product Class
    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }

    // Create static product list
    List<Product> products = new List<Product>()
    {
        new Product(){ Id=1, Name="Laptop", Price=55000 },
        new Product(){ Id=2, Name="Mouse", Price=500 },
        new Product(){ Id=3, Name="Keyboard", Price=1200 },
        new Product(){ Id=4, Name="Monitor", Price=8000 },
        new Product(){ Id=5, Name="Headphones", Price=1500 },
        new Product(){ Id=6, Name="Smartphone", Price=25000 }
    };

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            gvProducts.DataSource = products;
            gvProducts.DataBind();
        }
    }

    protected void btnSearch_Click(object sender, EventArgs e)
    {
        string searchValue = txtSearch.Text.Trim().ToLower();

        // Using Lambda + LINQ for filtering
        var filteredProducts = products.Where(p =>
            p.Name.ToLower().Contains(searchValue) ||
            p.Price.ToString().Contains(searchValue)
        ).ToList();

        gvProducts.DataSource = filteredProducts;
        gvProducts.DataBind();
    }}

5. Output Example

Before Search:
All products are listed in a grid.

User Enters “mouse”:

Grid shows only “Mouse” record.

User Enters “50000”:

Grid shows “Laptop” because price contains 55,000.

6. Real-Time Business Scenarios for LINQ & Lambda in WebForms

Scenario	Description
Product Filtering	Search/filter items dynamically
Reports Dashboard	Filter report data by date or range
Order Management	Find orders with specific status
Employee Portal	Search employees by name, ID, or department
Notification System	Filter users based on subscription type

7. Difference Between LINQ Query and Lambda Syntax

Type	Example	Notes
LINQ Query Syntax	from p in products where p.Price > 1000 select p;	SQL-like syntax
Lambda Expression Syntax	products.Where(p => p.Price > 1000);	Compact and faster

8. Advanced Example – Sorting & Aggregation

// Sort by Pricevar sortedProducts = products.OrderBy(p => p.Price).ToList();

// Get Average Pricevar avgPrice = products.Average(p => p.Price);

// Find Most Expensive Productvar maxProduct = products.OrderByDescending(p => p.Price).FirstOrDefault();

9. Advantages

Readable Code – Less boilerplate

Type Safety – Checked during compile-time

Performance – Optimized queries with deferred execution

Flexibility – Works with data from SQL, XML, or objects

Maintainability – One consistent syntax across all layers

10. Real-Time Example Flow Summary

Step	Action
User enters text in the search box	“mouse”
Button click triggers btnSearch_Click	Event fires
Lambda + LINQ filters data in memory	.Where(p => ...)
Result is bound to the GridView	UI updates instantly

11. Conclusion

Lambda Expressions and LINQ revolutionize the way you write data-driven code in ASP.NET Web Forms.
They transform multiple lines of loops, conditions, and filtering into clean, readable, and efficient code — all without touching SQL directly.

Whether you’re working with lists, databases, or DataTables, LINQ + Lambda makes your Web Forms application modern, faster, and easier to maintain.