加干扰字符

public class keyformat
    {
        /// <summary>
        /// 验证规则是否符合标准
        /// </summary>
        /// <param name="format">需要验证的字符串</param>
        public bool TestFormat(string format)
        {
            Boolean f = true;
            if (IsStr(format, @"[^@_\$\d]+"))
            {
                f = false;
            }
            else if (IsStr(format, @"[^_]\$"))
            {
                f = false;
            }
            //数字只能在$之后且数字在字符串最前
            else if (IsStr(format, @"[^\$]\d+|^\d+"))
            {
                f = false;
            }
            return f;
        }


        /// <summary>
        /// 将字符串按照format和key进行
        /// </summary>
        /// <param name="str">要整理的字符串</param>
        /// <param name="format">规则</param>
        /// <param name="key">加密用的字符串</param>
        /// <returns></returns>
        public string GetFkstring(string str, string format, string key)
        {
            StringBuilder result = new StringBuilder();
            if (TestFormat(format))
            {
                format = GetFormat(format);

                int j = 0, k = 0;
                for (int i = 0; ; i++)
                {
                    if (i == format.Length)
                    {
                        //规则先用完，先将字符串剩下的拼上，再将加密用的字符串拼上
                        result.Append(key.Substring(k));
                        if (j < str.Length)
                            result.Append(str.Substring(j));
                        break;
                    }

                    if (format[i] == '@')
                    {
                        //若用完用“ ”补足
                        if (j >= str.Length)
                            result.Append(" ");
                        else
                            result.Append(str[j]);
                        j++;
                    }
                    else
                    {
                        result.Append(key[k]);
                        k++;
                        if (k == key.Length)
                        {
                            //加密用的字符串不够，将字符串剩下的拼上
                            if (j < str.Length)
                                result.Append(str.Substring(j));
                            break;
                        }
                    }
                }
            }
            else
            {
                result.Append(str);
            }
            return result.ToString();
        }
        /// <summary>
        /// 将key中的$加数字转换为@和_
        /// </summary>
        /// <param name="format">需要转换的key</param>
        /// <returns></returns>
        private string GetFormat(string format)
        {
            if (TestFormat(format))
            {
                int n = format.LastIndexOf("_$");
                while (n > -1)
                {
                    string formatbefore = format.Substring(0, n + 1);
                    string formatafter = format.Substring(n + 2);

                    //取出$后面的数字并把formatafter中的数字截掉
                    int reReplaceN = 1;
                    string reReplaceNStr = MatchStr(formatafter, @"^(\d+)[@_]*");
                    if (reReplaceNStr != "")
                    {
                        reReplaceN = Int16.Parse(reReplaceNStr);
                        formatafter = formatafter.Substring(reReplaceNStr.Length);
                    }
                    //得到要重复的字段
                    //_$之前提一个@或$
                    int replaceIndex = Math.Max(formatbefore.LastIndexOf("@"), formatbefore.LastIndexOf("$"));
                    string replaceOne = "";
                    if (replaceIndex > -1)
                    {
                        replaceOne = formatbefore.Substring(replaceIndex);
                        //如果是$把$和数字(如果有)去掉
                        if (replaceOne[0] == '$')
                        {
                            replaceOne = replaceOne.Substring(replaceOne.IndexOf('_'));
                        }
                    }
                    //拼接
                    format = formatbefore + GetRepeatStr(replaceOne, reReplaceN) + formatafter;

                    n = format.LastIndexOf("_$");
                }
                return format.Replace("$", "");
            }
            return "";
        }

        /// <summary>
        /// 将字符串重复
        /// </summary>
        /// <param name="str">需要重复的字符串</param>
        /// <param name="n">重复的次数</param>
        /// <returns></returns>
        private string GetRepeatStr(string str, int n)
        {
            string result = "";
            for (int i = 0; i < n; i++)
            {
                result += str;
            }
            return result;
        }

        /// <summary>
        /// 根据正则找出匹配字符串
        /// </summary>
        /// <param name="input">需要验证的字符串</param>
        /// <param name="pattern">正则</param>
        /// <returns></returns>
        private string MatchStr(string input, string pattern)
        {
            string result = "";
            Regex r = new Regex(pattern);
            Match m = r.Match(input);
            if (m.Success)
            {
                result = m.Groups[1].ToString();
            }
            return result;
        }
        /// <summary>
        /// 根据正则验证字符串是否符合要求
        /// </summary>
        /// <param name="input">需要验证的字符串</param>
        /// <param name="pattern">正则</param>
        /// <returns></returns>
        private bool IsStr(string input, string pattern)
        {
            Regex r = new Regex(pattern);
            Match m = r.Match(input);
            return m.Success;
        }
        
    }