Helper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AppRTCDemo
{
    public static class Helper
    {
        private static readonly Random _rng = new Random();
        private const string _chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        /// <summary>
        /// generate random string
        /// </summary>
        /// <param name="size">size of generated string</param>
        /// <returns></returns>
        public static string RandomString(int size)
        {
            char[] buffer = new char[size];

            for (int i = 0; i < size; i++)
            {
                buffer[i] = _chars[_rng.Next(_chars.Length)];
            }
            return new string(buffer);
        }
    }

}