Let's write code to validate the phone number in a specific format using regex in C#. // Method to validate the phone number public static bool IsValidPhoneNumber(string PhoneNumber) { // Check if the input string is null or empty if (string.IsNullOrEmpty(PhoneNumber)) { // Return false if the phone number is null or empty return false; } // Define the regex pattern to match valid phone numbers in the formats // (222) 222-2222 and 222-222-2222 string pattern = @"^$?\d{3}$?[- ]?\d{3}[-]\d{4}$"; // Use Regex.IsMatch to check if the phone number matches the pattern // RegexOptions.Multiline is used to ensure the pattern is applied to each line if the input contains multiple lines return Regex.IsMatch(PhoneNumber, pattern, RegexOptions.Multiline); } Explanation: ^ asserts the position at the start of the string.$? optionally matches an opening parenthesis (.\d{3} matches exactly three digits.$? optionally matches a closing parenthesis ).[- ]? optionally matches a hyphen - or a space .\d{3} matches exactly three digits.[-] matches exactly a hyphen -.\d{4} matches exactly four digits.$ asserts the position at the end of the string. Now call this function using System; using System.Collections.Generic; using System.Text.RegularExpressions; namespace ConsoleApp1 { public class Program { public static void Main() { IListandlt;string> list = new Listandlt;string> { "(222) 222-2222", "222-222-2222", "124-125-4585", "996 748 8596", "7485965874", "(222) 222-2222", "222-222-2222", "123 456 7890", "222.222.2222" }; foreach (var item in list) { bool IsMatch = Program.IsValidPhoneNumber(item); Console.BackgroundColor = IsMatch ? ConsoleColor.DarkGreen : ConsoleColor.Red; Console.WriteLine(item + " " + IsMatch); Console.ResetColor(); } Console.ReadLine(); } } } Output : and and

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Valid Phone number

Steilla Mitchel 317 12-Jun-2024

Given a text file file.txt that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

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Updated on 12-Jun-2024

Steilla Mitchel

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I completed my post-graduation in 2013 in the engineering field. Engineering is the application of science and math to solve problems. Engineers figure out how things work and find practical uses for scientific discoveries. Scientists and inventors often get the credit for innovations that advance the human condition, but it is engineers who are instrumental in making those innovations available to the world. I love pet animals such as dogs, cats, etc.

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Ravi Vishwakarma

12-Jun-2024

Let's write code to validate the phone number in a specific format using regex in C#.

// Method to validate the phone number
        public static bool IsValidPhoneNumber(string PhoneNumber)
        {
            // Check if the input string is null or empty
            if (string.IsNullOrEmpty(PhoneNumber))
            {
                // Return false if the phone number is null or empty
                return false;
            }

            // Define the regex pattern to match valid phone numbers in the formats
            // (222) 222-2222 and 222-222-2222
            string pattern = @"^\(?\d{3}\)?[- ]?\d{3}[-]\d{4}$";

            // Use Regex.IsMatch to check if the phone number matches the pattern
            // RegexOptions.Multiline is used to ensure the pattern is applied to each line if the input contains multiple lines
            return Regex.IsMatch(PhoneNumber, pattern, RegexOptions.Multiline);
        }

Explanation:

^ asserts the position at the start of the string.
\(? optionally matches an opening parenthesis (.
\d{3} matches exactly three digits.
\)? optionally matches a closing parenthesis ).
[- ]? optionally matches a hyphen - or a space .
\d{3} matches exactly three digits.
[-] matches exactly a hyphen -.
\d{4} matches exactly four digits.
$ asserts the position at the end of the string.

Now call this function

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
namespace ConsoleApp1
{
    public class Program
    {
        public static void Main()
        {
            IList<string> list = new List<string>
            {
                "(222) 222-2222",
                "222-222-2222",
                "124-125-4585",
                "996 748 8596",
                "7485965874",
                "(222) 222-2222", "222-222-2222", "123 456 7890", "222.222.2222"
            };

			foreach (var item in list)
            {
                bool IsMatch = Program.IsValidPhoneNumber(item);

                Console.BackgroundColor = IsMatch ? ConsoleColor.DarkGreen : ConsoleColor.Red;

                Console.WriteLine(item + " " + IsMatch);
                Console.ResetColor();
            }

            Console.ReadLine();
        }
	}	
}

Output :

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Valid Phone number

Steilla Mitchel

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