using System.Text.RegularExpressions;

using System.Linq;

using System;

public class Program

{

    public static void Main()

    {

        // Validate if a string is a valid date format

        Regex validateDateRegex = new Regex("^[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}$");

        Console.WriteLine(validateDateRegex.IsMatch("12/12/2022"));  // prints True

        // Extract date from string

        Regex extractDateRegex = new Regex("[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}");

        string [] extracted = extractDateRegex.Matches("I\'m on vacation from 1/18/2021 till 1/29/2021")

            .Cast()

            .Select(m => m.Value) 

            .ToArray(); 

        Console.WriteLine(String.Join(",", extracted)); // prints 1/18/2021,1/29/2021

    }

}

using System.Text.RegularExpressions;

using System.Linq;

using System;

public class Program

{

    public static void Main()

    {

        // Validate if a string is a valid date format

        Regex validateDateRegex = new Regex("^[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}$");

        Console.WriteLine(validateDateRegex.IsMatch("12/12/2022"));  // prints True

        // Extract date from string

        Regex extractDateRegex = new Regex("[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}");

        string [] extracted = extractDateRegex.Matches("I\'m on vacation from 1/18/2021 till 1/29/2021")

            .Cast()

            .Select(m => m.Value) 

            .ToArray(); 

        Console.WriteLine(String.Join(",", extracted)); // prints 1/18/2021,1/29/2021

    }

}