C#生成不重复的N位随机数

直接上代码：

#region 生成N位随机数
        /// <summary>
        /// 生成N位随机数
        /// </summary>
        /// <param name="N">N位随机数</param>
        /// <returns>生成的N位随机数</returns>
        public static string RandCode(int N)
        {
            char[] arrChar = new char[] { '', '', '', '', '', '', '', '', '', '' };
            StringBuilder num = new StringBuilder();
            Random rnd = new Random(Guid.NewGuid().GetHashCode());
            for (int i = ; i < N; i++)
            {
                num.Append(arrChar[rnd.Next(, arrChar.Length)].ToString());
            }
            return num.ToString();
        }
        #endregion