C#

How to Use Arrays and Lists in ASP.NET C# WebForms

Introduction

In ASP.NET WebForms, you often need to handle multiple values — like product names, user IDs, or form inputs — together.
That’s where Arrays and Lists come in.

  • Arrays are fixed-size collections.

  • Lists are dynamic — you can add or remove items at runtime.

In this blog, we’ll understand both with real ASP.NET C# examples, such as displaying product names in a GridView.

What is an Array in C#?

An Array is a collection that stores multiple values of the same type in a fixed size.

Example

string[] products = { "Laptop", "Mouse", "Keyboard", "Monitor" };

You can access values using index positions:

Response.Write(products[0]); // Output: Laptop

Example 1: Display Array Data in ASP.NET WebForm

ASPX Page (ArrayExample.aspx)

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ArrayExample.aspx.cs" Inherits="WebFormsDemo.ArrayExample" %>

<!DOCTYPE html>
<html>
<head>
    <title>Array Example in ASP.NET</title>
</head>
<body>
    <h2>Array Example: Product List</h2>
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="true"></asp:GridView>
</body>
</html>

Code Behind (ArrayExample.aspx.cs)

using System;
using System.Data;

namespace WebFormsDemo
{
    public partial class ArrayExample : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            // Step 1: Create an array of products
            string[] products = { "Laptop", "Mouse", "Keyboard", "Monitor", "Printer" };

            // Step 2: Convert array to DataTable to display in GridView
            DataTable dt = new DataTable();
            dt.Columns.Add("Product Name");

            foreach (string item in products)
            {
                dt.Rows.Add(item);
            }

            // Step 3: Bind data to GridView
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }
    }
}

Output

Product Name
Laptop
Mouse
Keyboard
Monitor
Printer

What is a List in C#?

A List is a generic collection that allows dynamic resizing — you can add, remove, or modify elements easily.

Example

List<string> employees = new List<string>();
employees.Add("John");
employees.Add("Priya");

Example 2: Display List Data in ASP.NET WebForm

ASPX Page (ListExample.aspx)

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ListExample.aspx.cs" Inherits="WebFormsDemo.ListExample" %>

<!DOCTYPE html>
<html>
<head>
    <title>List Example in ASP.NET</title>
</head>
<body>
    <h2>List Example: Employee Details</h2>

    <asp:Button ID="btnAdd" runat="server" Text="Add New Employee" OnClick="btnAdd_Click" />
    <br /><br />
    <asp:GridView ID="GridViewEmployees" runat="server" AutoGenerateColumns="true"></asp:GridView>
</body>
</html>

Code Behind (ListExample.aspx.cs)

using System;
using System.Collections.Generic;
using System.Data;

namespace WebFormsDemo
{
    public partial class ListExample : System.Web.UI.Page
    {
        // Static list to hold employees (simulates session-based data)
        static List<string> employeeList = new List<string> { "Sandhiya", "Karthik", "Priya", "Mani" };

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindGrid();
            }
        }

        // Method to Bind List to GridView
        private void BindGrid()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Employee Name");

            foreach (string emp in employeeList)
            {
                dt.Rows.Add(emp);
            }

            GridViewEmployees.DataSource = dt;
            GridViewEmployees.DataBind();
        }

        // Add new employee dynamically
        protected void btnAdd_Click(object sender, EventArgs e)
        {
            employeeList.Add("New Employee " + (employeeList.Count + 1));
            BindGrid();
        }
    }
}

Output

Employee Name
Sandhiya
Karthik
Priya
Mani

When you click “Add New Employee”, a new employee is dynamically added to the list.

Real-Time Use Case: Arrays vs Lists in ASP.NET

ScenarioBest ChoiceReason
Fixed number of dropdown options (e.g., Gender, Country)ArraySimple, small data, fixed values
Dynamic data (e.g., Products, Employees)ListData can grow or shrink at runtime
Data binding from DB resultsList / DataTableEasy integration with LINQ or GridView
Temporary in-memory storageListSupports add/remove easily

Tip

If you’re loading data from a database:

List<string> productList = new List<string>();

using (SqlConnection con = new SqlConnection("your_connection_string"))
{
    SqlCommand cmd = new SqlCommand("SELECT ProductName FROM Products", con);
    con.Open();
    SqlDataReader reader = cmd.ExecuteReader();

    while (reader.Read())
    {
        productList.Add(reader["ProductName"].ToString());
    }
}

Then bind productList to a GridView or DropDownList.

Conclusion

Arrays and Lists are essential for handling collections of data in ASP.NET WebForms.

  • Use Arrays when your data is fixed-size and simple.

  • Use Lists when your data is dynamic and frequently changes.

Both integrate smoothly with ASP.NET controls like GridView, DropDownList, and Repeater.
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