using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;

namespace WindowsApplication1
{
    class XOREncrypt
    {
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="str">待加密的明文字符串</param>
        /// <param name="key">密钥</param>
        /// <returns>加密后的字符串</returns>
        public static string EncryptString(string str, string key)
        {
            byte[] bStr = (new UnicodeEncoding()).GetBytes(str);
            byte[] bKey = (new UnicodeEncoding()).GetBytes(key);

            for (int i = 0; i < bStr.Length; i += 2)
            {
                for (int j = 0; j < bKey.Length; j += 2)
                {
                    bStr[i] = Convert.ToByte(bStr[i] ^ bKey[j]);
                }
            }

            return (new UnicodeEncoding()).GetString(bStr).TrimEnd('\0');
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="str">待解密的密文字符串</param>
        /// <param name="key">密钥</param>
        /// <returns>解密后的明文</returns>
        public static string DecryptString(string str, string key)
        {
            return EncryptString(str, key);
        }
    }
}

<add key="ConnStr" value="&gt;(?;(?p&#x15;&#x4;&#xC;&#x2;&#x5;&#x18;&#xC;&#x1A;&#x11;&#x1E;&#x1C;&#x1;&#x8;&#x15;&#x1D;&#x1F;&#x8;&#x1E;&#x1E;v&#x19;?8&gt;9()&#x12;&#xE;&quot;##(.9$&quot;#p4(&gt;v),9,/,&gt;(p.,!!.(?#9(?v&#x18;&gt;(?p&gt;,v&#x1D;,&gt;&gt;:&quot;?)p:,#*+8'$#v" />

sqlOp.ConnStr = XOREncrypt.DecryptString(sqlOp.ConnStr, "cr0_3");