using System;

using System.Text.RegularExpressions;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var data = "[20,8,25,5,34,12]";

        int[] result = ParseNumbersList(data);

        foreach (var s in result) {

            Console.WriteLine(s);

        }

    }

    public static int[] ParseNumbersList(string input) {

        const char valueSeperator = ',';

        var removeBrackets = input.Substring(1, input.Length-2);

        var parts = removeBrackets.Split(valueSeperator);

        return parts.Select(p => int.Parse(p)).ToArray();

    }

}

​

​