保存emoji到数据库

 /// <summary>  
        /// <summary>  
        /// 字符串转Unicode  
        /// </summary>  
        /// <param name="source">源字符串</param>  
        /// <returns>Unicode编码后的字符串</returns>  
        public static string String2Unicode(string source)
        {
            byte[] bytes = Encoding.Unicode.GetBytes(source);
            StringBuilder stringBuilder = new StringBuilder();
            for (int i = 0; i < bytes.Length; i += 2)
            {
                stringBuilder.AppendFormat("\\u{0}{1}", bytes[i + 1].ToString("x").PadLeft(2, '0'), bytes[i].ToString("x").PadLeft(2, '0'));
            }
            return stringBuilder.ToString();
        }

        /// <summary>  
        /// Unicode转字符串  
        /// </summary>  
        /// <param name="source">经过Unicode编码的字符串</param>  
        /// <returns>正常字符串</returns>  
        public static string Unicode2String(string source)
        {
            return new Regex(@"\\u([0-9A-F]{4})", RegexOptions.IgnoreCase | RegexOptions.Compiled).Replace(
                         source, x => string.Empty + Convert.ToChar(Convert.ToUInt16(x.Result("$1"), 16)));
        }