Mask an Aadhar Number into Blocks of 4 Digits Each

using System;
using System.Text;

namespace Adhar_no
{
    class Program
    {
        public static string MaskAadharNumber(string aadharNumber)
        {
            if (aadharNumber.Length != 12)
            {
                throw new ArgumentException("Aadhar number must be exactly 12 digits long.");
            }
            // Mask the Aadhar number
            StringBuilder masked = new StringBuilder();
            for (int i = 0; i < 12; i++)
            {
                // Insert a space every 4 digits, except at the end
                if (i > 0 && i % 4 == 0)
                {
                    masked.Append(" ");
                }
                masked.Append(aadharNumber[i]);
            }
            return masked.ToString();
        }
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Enter Aadhar Number Here.");
                string aadharNumber = Console.ReadLine();
                string maskedAadhar = MaskAadharNumber(aadharNumber);
                Console.WriteLine("Masked Aadhar Number: " + maskedAadhar);
            }
            catch (ArgumentException ex)
            {
                Console.WriteLine("Error: " + ex.Message);
            }
            Console.Read();
        }
    }
}

Here we use

1. Argument Validation: Check if the Aadhar number provided is exactly 12 digits long. If not, it throws an argument exception.
   
2. StringBuilder Initialization: Initializes a StringBuilder object named masked to build the masked Aadhar number.
3. Loop through Aadhar Number: Iterates through each character of the Aadhar number string.
4. Insert Spaces: Inserts a space (" ") every 4 characters to create blocks of 4 digits.
5. Return Masked Aadhar Number: Returns the final masked Aadhar number as a string.

Final Output

Mask an Account no in c#

In C#, you can use a masked account number.

1. _Substring_

Extract the last few digits of the account number and mask the rest.

string accountNumber = "1234567890";
string maskedNumber = accountNumber.Substring(0, accountNumber.Length - 4) + "****";
Console.WriteLine(maskedNumber); // Output: 123456****

2. _Regex_

Use regular expressions to replace all but the last few digits with a mask.

string accountNumber = "1234567890";
string maskedNumber = System.Text.RegularExpressions.Regex.Replace(
    accountNumber, 
    @"^(\d{6})(\d{4})$", 
    "$1****"
);
Console.WriteLine(maskedNumber);  // Output: 123456****

3. _String.Format_

Use string formatting to display the account number with a mask.

string accountNumber = "1234567890";
string maskedNumber = string.Format("{0:####-****}", Convert.ToInt64(accountNumber));
Console.WriteLine(maskedNumber);  // Output: 1234-****

4. Masked an Adhar Number Last Four Digit

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
namespace maskadharcard
{
    class Program
    {
        static void Main(string[] args)
        {
            string cardNumber = "345612343456";
            var cardNumber1 = string.Format("########{0}", cardNumber.Substring(8, 4));
            var maskedCardNumberWithSpaces = Regex.Replace(cardNumber1, ".{4}", "$0 ");
            Console.WriteLine(maskedCardNumberWithSpaces);
            Console.Read();
        }
    }
}

Output. Finally, a screen is shown.