maskname.cs

        /// <summary>
        /// 遮罩名字
        /// </summary>
        /// <param name="name">原始姓名</param>
        /// <param name="keepStart">保留開頭幾個字</param>
        /// <param name="keepEnd">保留結尾幾個字</param>
        /// <returns>遮罩後的姓名</returns>
        public static string MaskName(string name, int keepStart = 1, int keepEnd = 1)
        {
            if (string.IsNullOrEmpty(name)) return name;

            int length = name.Length;

            // 如果總長度 <= 要保留的字數，不做遮罩
            if (length <= keepStart + keepEnd) return name;

            // 中間需要遮罩的字數
            int maskCount = length - keepStart - keepEnd;
            string mask = new string('●', maskCount);

            // 拼接
            return name.Substring(0, keepStart) + mask + name.Substring(length - keepEnd, keepEnd);
        }
        
        
        //Result:
        //MaskName("許當麻");   // 結果：許●麻
        //MaskName("當麻");     // 結果：當●
        //MaskName("許當麻",2,0) // 結果: 許當●
        //MaskName("當麻", 0, 1) // 結果: ●麻