Question

C#

Create a console application that prompts the user to enter a regular expression, and then prompts the user to enter some input and compare the two for a match until the user presses Esc:

The default regular expression checks for at least one digit.
Enter a regular expression (or press ENTER to use the default): ^[a- z]+$
Enter some input: apples
apples matches ^[a-z]+$? True
Press ESC to end or any key to try again.
Enter a regular expression (or press ENTER to use the default): ^[a- z]+$
Enter some input: abc123xyz
abc123xyz matches ^[a-z]+$? False
Press ESC to end or any key to try again.

Answer 1

Code:

using System;
using System.Text.RegularExpressions;

namespace regExpressionConsole
{
class Program
{

static ConsoleKeyInfo ckey;

// console key class is used to determine the entered key is esc or not

static void Main(string[] args)
{
String expression;
  
do

{
Console.WriteLine("Enter a regular expression (or press ENTER to use the default): ^[a- z]+$");
//Get user input expression if any   

string res = Console.ReadLine();

//check whether they entered enter key or not

if(res=="")
{
expression = "^[a-z]+$";
}
else
{
expression = res;

}

//get user input values to compare with the expression

Console.WriteLine("Enter some input ");
string input;
input = Console.ReadLine();

//Matching with the values and expression

var match = Regex.Match(input, expression);

if (match.Success)
{
Console.WriteLine("True");
}
else
{
Console.WriteLine("False");
}

//Confirm whether user ending the application or continuing.

Console.WriteLine("Press Escape to end or any key to try again..");
ckey = Console.ReadKey();

}
while (ckey.Key != ConsoleKey.Escape);

}
}
}

Output: