Find the frequency of each character in a string

Sandhiya Priya
Oct 31
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Article

Step 1: Design Page – CharacterFrequency.aspx

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

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Character Frequency in a String - Real Time Example</title>
    <style>
        body {
            font-family: Arial;
            background-color: #f0f2f5;
            margin: 50px;
        }
        .container {
            width: 500px;
            margin: auto;
            background: white;
            border-radius: 8px;
            box-shadow: 0px 0px 10px #ccc;
            padding: 25px;
        }
        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;
            margin-top: 10px;
            border-radius: 5px;
            cursor: pointer;
            width: 100%;
        }
        .result {
            margin-top: 20px;
            font-weight: bold;
            color: #333;
            text-align: center;
            white-space: pre-line;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <div class="container">
            <h2>Find Frequency of Each Character</h2>

            <asp:Label ID="lblInput" runat="server" Text="Enter a String:"></asp:Label><br />
            <asp:TextBox ID="txtInput" runat="server" CssClass="form-control" placeholder="Example: programming"></asp:TextBox><br />

            <asp:Button ID="btnFind" runat="server" Text="Find Frequency" CssClass="btn" OnClick="btnFind_Click" /><br />

            <asp:Label ID="lblResult" runat="server" CssClass="result"></asp:Label>
        </div>
    </form>
</body>
</html>

Step 2: Backend Logic – CharacterFrequency.aspx.cs

using System;
using System.Collections.Generic;

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

    protected void btnFind_Click(object sender, EventArgs e)
    {
        string input = txtInput.Text.Trim().ToLower();

        if (string.IsNullOrEmpty(input))
        {
            lblResult.Text = "Please enter a valid string.";
            lblResult.ForeColor = System.Drawing.Color.Red;
            return;
        }

        Dictionary<char, int> charCount = new Dictionary<char, int>();

        // Count frequency of each character
        foreach (char c in input)
        {
            if (char.IsLetterOrDigit(c)) // count only letters and digits
            {
                if (charCount.ContainsKey(c))
                    charCount[c]++;
                else
                    charCount[c] = 1;
            }
        }

        // Display the result
        string result = "Character Frequency:\n";
        foreach (var item in charCount)
        {
            result += $"'{item.Key}' = {item.Value}\n";
        }

        lblResult.Text = result;
        lblResult.ForeColor = System.Drawing.Color.DarkBlue;
    }
}

Real-Time Example Flow

Open CharacterFrequency.aspx in your browser.
Enter: programming
Click “Find Frequency”

Output will be displayed as:

Character Frequency:
'p' = 1
'r' = 2
'o' = 1
'g' = 2
'a' = 1
'm' = 2
'i' = 1
'n' = 1

Explanation

Step	Description
1	Get the user input string from the TextBox.
2	Convert to lowercase to make counting case-insensitive.
3	Use a Dictionary to count each character’s frequency.
4	Display all character counts in a readable format.

Example Input / Output Table

Input	Output
programming	p=1, r=2, o=1, g=2, a=1, m=2, i=1, n=1
hello	h=1, e=1, l=2, o=1
success	s=3, u=1, c=2, e=1
webforms	w=1, e=1, b=1, f=1, o=1, r=1, m=1, s=1
sandhiya	s=1, a=2, n=1, d=1, h=1, i=1, y=1