关键代码：

using System;
using System.Text;

namespace YanZhiwei.DotNet2.Utilities.Common
{
    /// <summary>
    ///Random的帮助类
    /// </summary>
    public static class RandomHelper
    {
        #region 生成设置范围内的Double的随机数
        /// <summary>
        /// 生成设置范围内的Double的随机数
        ///<para>eg:RandomHelper.NextDouble(1.5, 1.7);</para> 
        /// </summary>
        /// <param name="miniDouble">生成随机数的最大值</param>
        /// <param name="maxiDouble">生成随机数的最小值</param>
        /// <returns>Double的随机数</returns>
        public static double NextDouble(double miniDouble, double maxiDouble)
        {
            Random _random = new Random((int)(DateTime.Now.Ticks));
            return _random.NextDouble() * (maxiDouble - miniDouble) + miniDouble;
        }
        #endregion
        #region 生成随机字符串
        /// <summary>
        /// 生成随机字符串
        /// <para>RandomHelper.NetxtString(4, false);</para>
        /// </summary>
        /// <param name="size">字符串长度</param>
        /// <param name="lowerCase">字符串是小写</param>
        /// <returns>随机字符串</returns>
        public static string NetxtString(int size, bool lowerCase)
        {
            Random _random = new Random((int)(DateTime.Now.Ticks));
            StringBuilder _builder = new StringBuilder(size);
            int _startChar = lowerCase ? 97 : 65;//65 = A / 97 = a
            for (int i = 0; i < size; i++)
                _builder.Append((char)(26 * _random.NextDouble() + _startChar));
            return _builder.ToString();
        }
        #endregion
        #region  0~9 A~Z字符串
        /// <summary>
        /// 0~9 A~Z字符串
        /// </summary>
        public static string RandomString_09AZ = "0123456789ABCDEFGHIJKMLNOPQRSTUVWXYZ";
        #endregion
        #region 依据指定字符串来生成随机字符串
        /// <summary>
        /// 依据指定字符串来生成随机字符串
        /// <para>RandomHelper.NetxtString(RandomHelper.RandomString_09AZ, 4, false);</para>
        /// </summary>
        /// <param name="randomString">指定字符串</param>
        /// <param name="size">字符串长度</param>
        /// <param name="lowerCase">字符串是小写</param>
        /// <returns>随机字符串</returns>
        public static string NetxtString(string randomString, int size, bool lowerCase)
        {
            string _nextString = string.Empty;
            Random _random = new Random((int)(DateTime.Now.Ticks));
            if (!string.IsNullOrEmpty(randomString))
            {
                StringBuilder _builder = new StringBuilder(size);
                int _maxCount = randomString.Length - 1;
                for (int i = 0; i < size; i++)
                {
                    int _number = _random.Next(0, _maxCount);
                    _builder.Append(randomString[_number]);
                }
                _nextString = _builder.ToString();
            }
            return lowerCase ? _nextString.ToLower() : _nextString.ToUpper();
        }
        #endregion
        #region 生成随机时间
        /// <summary>
        /// 生成随机时间
        /// <para>RandomHelper.NextDateTime();</para>
        /// </summary>
        /// <returns>随机时间</returns>
        public static DateTime NextDateTime()
        {
            Random _random = new Random((int)(DateTime.Now.Ticks));
            int _hour = _random.Next(2, 5);
            int _minute = _random.Next(0, 60);
            int _second = _random.Next(0, 60);
            string _dateTimeString = string.Format("{0} {1}:{2}:{3}", DateTime.Now.ToString("yyyy-MM-dd"), _hour, _minute, _second);
            DateTime _nextTime = Convert.ToDateTime(_dateTimeString);
            return _nextTime;
        }
        #endregion
        #region  生成随机MAC地址
        /// <summary>
        /// 生成随机MAC地址
        /// <para>RandomHelper.NextMacAddress();</para>
        /// </summary>
        /// <returns>新的MAC地址</returns>
        public static string NextMacAddress()
        {
            int _minValue = 0, _maxValue = 16;
            Random _random = new Random((int)(DateTime.Now.Ticks));
            string _newMacAddress = string.Format("{0}{1}:{2}{3}:{4}{5}:{6}{7}:{8}{9}:{10}{11}",
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x"),
               _random.Next(_minValue, _maxValue).ToString("x")
                ).ToUpper();
            return _newMacAddress;
        }
        #endregion
    }
}