using System;

using System.Globalization;

using System.Text.RegularExpressions;

​

public class Example

{

   public static void Main()

   {

       var data = "[22]";

       string pattern = @"(\d+)";

       var m = Regex.Match(data, pattern);

       if (m.Success)

       {

            Console.WriteLine(int.Parse(((m.Groups[0]).Captures[0]).Value));

       }

   }

}