Reverse a number

Sandhiya Priya
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Article

Step 1: Design the WebForm (ReverseNumber.aspx)

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

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Reverse Number - Real Time Example</title>
    <style>
        body {
            font-family: Arial;
            background-color: #f0f2f5;
            margin: 50px;
        }
        .container {
            width: 400px;
            margin: auto;
            background: white;
            border-radius: 8px;
            box-shadow: 0px 0px 10px #ccc;
            padding: 20px;
        }
        h2 {
            color: #1A2A80;
            text-align: center;
        }
        .form-control {
            width: 100%;
            padding: 8px;
            margin-top: 10px;
        }
        .btn {
            background-color: #7A85C1;
            color: white;
            border: none;
            padding: 10px 20px;
            margin-top: 10px;
            border-radius: 5px;
            cursor: pointer;
        }
        .result {
            font-weight: bold;
            color: #333;
            margin-top: 15px;
            text-align: center;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <div class="container">
            <h2>Reverse Number Program</h2>
            <asp:Label ID="lblNumber" runat="server" Text="Enter a Number:"></asp:Label><br />
            <asp:TextBox ID="txtNumber" runat="server" CssClass="form-control"></asp:TextBox><br />
            <asp:Button ID="btnReverse" runat="server" Text="Reverse Number" CssClass="btn" OnClick="btnReverse_Click" /><br />
            <asp:Label ID="lblResult" runat="server" CssClass="result"></asp:Label>
        </div>
    </form>
</body>
</html>

Step 2: Backend Logic (ReverseNumber.aspx.cs)

using System;

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

    protected void btnReverse_Click(object sender, EventArgs e)
    {
        int number;
        bool isValid = int.TryParse(txtNumber.Text.Trim(), out number);

        if (!isValid || number < 0)
        {
            lblResult.Text = "Please enter a valid positive number.";
            lblResult.ForeColor = System.Drawing.Color.Red;
            return;
        }

        int reversed = ReverseNumberLogic(number);
        lblResult.Text = $"The reverse of {number} is {reversed}.";
        lblResult.ForeColor = System.Drawing.Color.Green;
    }

    private int ReverseNumberLogic(int num)
    {
        int reversed = 0;
        while (num > 0)
        {
            int digit = num % 10;       // Get last digit
            reversed = (reversed * 10) + digit; // Append digit
            num /= 10;                  // Remove last digit
        }
        return reversed;
    }
}

Real-Time Example Flow

Open the web page ReverseNumber.aspx.
Enter a number, for example 4567.
Click “Reverse Number”.
Output will display:

“The reverse of 4567 is 7654.”

Explanation

Component	Purpose
TextBox (txtNumber)	To accept the user’s input number.
Button (btnReverse)	To trigger the reverse operation.
Label (lblResult)	Displays the reversed number result dynamically.
ReverseNumberLogic()	Uses modulus (%) and division (/) to reverse digits.

Sample Input / Output

Input	Output
123	321
560	65
9001	1009