using System;

using System.Linq;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program

{

      public class IndexMatches

        {

            public int Index { get; set; }

            public int IndexValuelength { get; set; }

        }

    public static void Main()

    {

            string maskiput = "xxxxxxxxxx56xxxxxx24xxxx";

​

            string inputvalue = "asadaddsdzasdsdsd31sds";

​

​

            System.Text.RegularExpressions.Regex re = new Regex(@"\d+");

            //Regex 

            List<IndexMatches> numberIndexes = re.Matches(maskiput).Cast<Match>().Select(k => new IndexMatches

            {

                Index = k.Index,

                IndexValuelength = k.Value.Length

            }).ToList();

​

​

​

            foreach (IndexMatches item in numberIndexes)

            {

                string result = inputvalue.Substring(item.Index-1, item.IndexValuelength);

                Console.WriteLine(result);

            }

    }

}