public static string GetRandomString(int size)
        {
            try
            {
                var chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
                var data = new byte[1];
                var crypto = new RNGCryptoServiceProvider();
                crypto.GetNonZeroBytes(data);
                data = new byte[size];
                crypto.GetNonZeroBytes(data);
                var result = new StringBuilder(size);
                foreach (byte b in data)
                {
                    result.Append(chars[b % (chars.Length - 1)]);
                }
                return result.ToString();
            }
            catch (Exception e)
            {
                Logging.WriteError("GetRandomString(int maxSize): " + e);
            }
            return "abcdef";
        }

        private static readonly Random _random = new Random(unchecked((int)DateTime.Now.Ticks));
        /// <summary>
        ///   Return Random number.
        /// </summary>
        /// <param name="from"> </param>
        /// <param name="to"> </param>
        /// <returns> </returns>
        public static int Random(int from, int to)
        {
            try
            {
                return _random.Next(from, to + 1);
            }
            catch (Exception exception)
            {
                Logging.WriteError("Random(int from, int to): " + exception);
            }
            return 0;
        }




        UTILISATION:
        string text = GetRandomString(Random(10,50));
        string text2 = GetRandomString(50);