1、进入微信公众号后台设置微信服务器配置参数（注意：Token和EncodingAESKey必须和微信服务器验证参数保持一致，不然验证不会通过）。

2、设置为安全模式

3、代码实现（主要分为验证接口和消息处理接口）：

1 /// 
 2 /// 验证接口 3 /// 
 4 /// 签名 5 /// 时间戳 6 ///  7 ///  8 /// 
      9 [HttpGet, Route("Message")]10 [AllowAnonymous]11 public ActionResult MessageGet(string signature, string timestamp, string nonce, string echostr)12 {13 if (new SecurityHelper().CheckSignature(signature, timestamp, nonce, _settings.Value.Token))14 {15 return Content(echostr);16 }17 return Content("");18 }19 20 /// 
21 /// 接收消息并处理和返回相应结果22 /// 
23 /// 当加密模式时才会有该变量（消息签名）24 /// 签名25 /// 时间戳26 /// 27 /// 
     28 [HttpPost, Route("Message")]29 [AllowAnonymous]30 public ActionResult MessagePost(string msg_signature, string signature, string timestamp, string nonce)31 {32 try33 {34 if (!new SecurityHelper().CheckSignature(signature, timestamp, nonce, _settings.Value.Token))35 {36 return Content(null);37 }38 using (Stream stream = HttpContext.Request.Body)39 {40 byte[] buffer = new byte[HttpContext.Request.ContentLength.Value];41 stream.Read(buffer, 0, buffer.Length);42 string content = Encoding.UTF8.GetString(buffer);43 if (!string.IsNullOrWhiteSpace(msg_signature)) // 消息加密模式44 {45 string decryptMsg = string.Empty;46 var wxBizMsgCrypt = new WXBizMsgCrypt(_settings.Value.Token, _settings.Value.EncodingAESKey, _settings.Value.AppId);47 int decryptResult = wxBizMsgCrypt.DecryptMsg(msg_signature, timestamp, nonce, content, ref decryptMsg);48 if (decryptResult == 0 && !string.IsNullOrWhiteSpace(decryptMsg))49 {50 string resultMsg = new WechatMessageHelper().MessageResult(decryptMsg);51 string sEncryptMsg = string.Empty;52 if (!string.IsNullOrWhiteSpace(resultMsg))53 {54 int encryptResult = wxBizMsgCrypt.EncryptMsg(resultMsg, timestamp, nonce, ref sEncryptMsg);55 if (encryptResult == 0 && !string.IsNullOrWhiteSpace(sEncryptMsg))56 {57 return Content(sEncryptMsg);58 }59 }60 }61 }62 else // 消息未加密码处理63 {64 string resultMsg = new WechatMessageHelper().MessageResult(content);65 return Content(resultMsg);66 }67 return Content(null);68 }69 }70 catch (Exception ex)71 {72 _logger.LogError("接收消息并处理和返回相应结果异常：", ex);73 return Content(null);74 }75 }

加解密实现（微信公众号官网有源码）

1 using System;  2 using System.Collections;  3 using System.Security.Cryptography;  4 using System.Text;  5 using System.Xml;  6   7 //-40001 ： 签名验证错误  8 //-40002 :  xml解析失败  9 //-40003 :  sha加密生成签名失败 10 //-40004 :  AESKey 非法 11 //-40005 :  appid 校验错误 12 //-40006 :  AES 加密失败 13 //-40007 ： AES 解密失败 14 //-40008 ： 解密后得到的buffer非法 15 //-40009 :  base64加密异常 16 //-40010 :  base64解密异常 17 namespace  Core.Common.Wechat 18 { 19     public class WXBizMsgCrypt 20     { 21         string m_sToken; 22         string m_sEncodingAESKey; 23         string m_sAppID; 24         enum WXBizMsgCryptErrorCode 25         { 26             WXBizMsgCrypt_OK = 0, 27             WXBizMsgCrypt_ValidateSignature_Error = -40001, 28             WXBizMsgCrypt_ParseXml_Error = -40002, 29             WXBizMsgCrypt_ComputeSignature_Error = -40003, 30             WXBizMsgCrypt_IllegalAesKey = -40004, 31             WXBizMsgCrypt_ValidateAppid_Error = -40005, 32             WXBizMsgCrypt_EncryptAES_Error = -40006, 33             WXBizMsgCrypt_DecryptAES_Error = -40007, 34             WXBizMsgCrypt_IllegalBuffer = -40008, 35             WXBizMsgCrypt_EncodeBase64_Error = -40009, 36             WXBizMsgCrypt_DecodeBase64_Error = -40010 37         }; 38  39         //构造函数 40         // @param sToken: 公众平台上，开发者设置的Token 41         // @param sEncodingAESKey: 公众平台上，开发者设置的EncodingAESKey 42         // @param sAppID: 公众帐号的appid 43         public WXBizMsgCrypt(string sToken, string sEncodingAESKey, string sAppID) 44         { 45             m_sToken = sToken; 46             m_sAppID = sAppID; 47             m_sEncodingAESKey = sEncodingAESKey; 48         } 49  50  51         // 检验消息的真实性，并且获取解密后的明文 52         // @param sMsgSignature: 签名串，对应URL参数的msg_signature 53         // @param sTimeStamp: 时间戳，对应URL参数的timestamp 54         // @param sNonce: 随机串，对应URL参数的nonce 55         // @param sPostData: 密文，对应POST请求的数据 56         // @param sMsg: 解密后的原文，当return返回0时有效 57         // @return: 成功0，失败返回对应的错误码 58         public int DecryptMsg(string sMsgSignature, string sTimeStamp, string sNonce, string sPostData, ref string sMsg) 59         { 60             if (m_sEncodingAESKey.Length != 43) 61             { 62                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_IllegalAesKey; 63             } 64             XmlDocument doc = new XmlDocument(); 65             XmlNode root; 66             string sEncryptMsg; 67             try 68             { 69                 doc.LoadXml(sPostData); 70                 root = doc.FirstChild; 71                 sEncryptMsg = root["Encrypt"].InnerText; 72             } 73             catch (Exception) 74             { 75                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ParseXml_Error; 76             } 77             //verify signature 78             int ret = 0; 79             ret = VerifySignature(m_sToken, sTimeStamp, sNonce, sEncryptMsg, sMsgSignature); 80             if (ret != 0) 81                 return ret; 82             //decrypt 83             string cpid = ""; 84             try 85             { 86                 sMsg = Cryptography.AES_decrypt(sEncryptMsg, m_sEncodingAESKey, ref cpid); 87             } 88             catch (FormatException) 89             { 90                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_DecodeBase64_Error; 91             } 92             catch (Exception) 93             { 94                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_DecryptAES_Error; 95             } 96             if (cpid != m_sAppID) 97                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ValidateAppid_Error; 98             return 0; 99         }100 101         //将企业号回复用户的消息加密打包102         // @param sReplyMsg: 企业号待回复用户的消息，xml格式的字符串103         // @param sTimeStamp: 时间戳，可以自己生成，也可以用URL参数的timestamp104         // @param sNonce: 随机串，可以自己生成，也可以用URL参数的nonce105         // @param sEncryptMsg: 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串,106         //                        当return返回0时有效107         // return：成功0，失败返回对应的错误码108         public int EncryptMsg(string sReplyMsg, string sTimeStamp, string sNonce, ref string sEncryptMsg)109         {110             if (m_sEncodingAESKey.Length != 43)111             {112                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_IllegalAesKey;113             }114             string raw = "";115             try116             {117                 raw = Cryptography.AES_encrypt(sReplyMsg, m_sEncodingAESKey, m_sAppID);118             }119             catch (Exception)120             {121                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_EncryptAES_Error;122             }123             string MsgSigature = "";124             int ret = 0;125             ret = GenarateSinature(m_sToken, sTimeStamp, sNonce, raw, ref MsgSigature);126             if (0 != ret)127                 return ret;128             sEncryptMsg = "";129 130             string EncryptLabelHead = "
     
     ";132             string MsgSigLabelHead = "
     
     ";134             string TimeStampLabelHead = "
     
     ";136             string NonceLabelHead = "
     
     ";138             sEncryptMsg = sEncryptMsg + "
     
      " + EncryptLabelHead + raw + EncryptLabelTail;139             sEncryptMsg = sEncryptMsg + MsgSigLabelHead + MsgSigature + MsgSigLabelTail;140             sEncryptMsg = sEncryptMsg + TimeStampLabelHead + sTimeStamp + TimeStampLabelTail;141             sEncryptMsg = sEncryptMsg + NonceLabelHead + sNonce + NonceLabelTail;142             sEncryptMsg += "
     ";143             return 0;144         }145 146         public class DictionarySort : System.Collections.IComparer147         {148             public int Compare(object oLeft, object oRight)149             {150                 string sLeft = oLeft as string;151                 string sRight = oRight as string;152                 int iLeftLength = sLeft.Length;153                 int iRightLength = sRight.Length;154                 int index = 0;155                 while (index < iLeftLength && index < iRightLength)156                 {157                     if (sLeft[index] < sRight[index])158                         return -1;159                     else if (sLeft[index] > sRight[index])160                         return 1;161                     else162                         index++;163                 }164                 return iLeftLength - iRightLength;165 166             }167         }168         //Verify Signature169         private static int VerifySignature(string sToken, string sTimeStamp, string sNonce, string sMsgEncrypt, string sSigture)170         {171             string hash = "";172             int ret = 0;173             ret = GenarateSinature(sToken, sTimeStamp, sNonce, sMsgEncrypt, ref hash);174             if (ret != 0)175                 return ret;176             //System.Console.WriteLine(hash);177             if (hash == sSigture)178                 return 0;179             else180             {181                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ValidateSignature_Error;182             }183         }184 185         public static int GenarateSinature(string sToken, string sTimeStamp, string sNonce, string sMsgEncrypt, ref string sMsgSignature)186         {187             ArrayList AL = new ArrayList();188             AL.Add(sToken);189             AL.Add(sTimeStamp);190             AL.Add(sNonce);191             AL.Add(sMsgEncrypt);192             AL.Sort(new DictionarySort());193             string raw = "";194             for (int i = 0; i < AL.Count; ++i)195             {196                 raw += AL[i];197             }198 199             SHA1 sha;200             ASCIIEncoding enc;201             string hash = "";202             try203             {204                 sha = new SHA1CryptoServiceProvider();205                 enc = new ASCIIEncoding();206                 byte[] dataToHash = enc.GetBytes(raw);207                 byte[] dataHashed = sha.ComputeHash(dataToHash);208                 hash = BitConverter.ToString(dataHashed).Replace("-", "");209                 hash = hash.ToLower();210             }211             catch (Exception)212             {213                 return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ComputeSignature_Error;214             }215             sMsgSignature = hash;216             return 0;217         }218     }219 }

1 using System;  2 using System.IO;  3 using System.Net;  4 using System.Security.Cryptography;  5 using System.Text;  6   7 namespace  Core.Common.Wechat  8 {  9     /// 
 10     ///  11     /// 
 12     public class Cryptography 13     { 14         public static UInt32 HostToNetworkOrder(UInt32 inval) 15         { 16             UInt32 outval = 0; 17             for (int i = 0; i < 4; i++) 18                 outval = (outval << 8) + ((inval >> (i * 8)) & 255); 19             return outval; 20         } 21  22         public static Int32 HostToNetworkOrder(Int32 inval) 23         { 24             Int32 outval = 0; 25             for (int i = 0; i < 4; i++) 26                 outval = (outval << 8) + ((inval >> (i * 8)) & 255); 27             return outval; 28         } 29         /// 
 30         /// 解密方法 31         /// 
 32         /// 密文 33         ///  34         /// 
      35         ///  36         public static string AES_decrypt(String Input, string EncodingAESKey, ref string appid) 37         { 38             byte[] Key; 39             Key = Convert.FromBase64String(EncodingAESKey + "="); 40             byte[] Iv = new byte[16]; 41             Array.Copy(Key, Iv, 16); 42             byte[] btmpMsg = AES_decrypt(Input, Iv, Key); 43  44             int len = BitConverter.ToInt32(btmpMsg, 16); 45             len = IPAddress.NetworkToHostOrder(len); 46  47  48             byte[] bMsg = new byte[len]; 49             byte[] bAppid = new byte[btmpMsg.Length - 20 - len]; 50             Array.Copy(btmpMsg, 20, bMsg, 0, len); 51             Array.Copy(btmpMsg, 20 + len, bAppid, 0, btmpMsg.Length - 20 - len); 52             string oriMsg = Encoding.UTF8.GetString(bMsg); 53             appid = Encoding.UTF8.GetString(bAppid); 54  55  56             return oriMsg; 57         } 58  59         public static String AES_encrypt(String Input, string EncodingAESKey, string appid) 60         { 61             byte[] Key; 62             Key = Convert.FromBase64String(EncodingAESKey + "="); 63             byte[] Iv = new byte[16]; 64             Array.Copy(Key, Iv, 16); 65             string Randcode = CreateRandCode(16); 66             byte[] bRand = Encoding.UTF8.GetBytes(Randcode); 67             byte[] bAppid = Encoding.UTF8.GetBytes(appid); 68             byte[] btmpMsg = Encoding.UTF8.GetBytes(Input); 69             byte[] bMsgLen = BitConverter.GetBytes(HostToNetworkOrder(btmpMsg.Length)); 70             byte[] bMsg = new byte[bRand.Length + bMsgLen.Length + bAppid.Length + btmpMsg.Length]; 71  72             Array.Copy(bRand, bMsg, bRand.Length); 73             Array.Copy(bMsgLen, 0, bMsg, bRand.Length, bMsgLen.Length); 74             Array.Copy(btmpMsg, 0, bMsg, bRand.Length + bMsgLen.Length, btmpMsg.Length); 75             Array.Copy(bAppid, 0, bMsg, bRand.Length + bMsgLen.Length + btmpMsg.Length, bAppid.Length); 76  77             return AES_encrypt(bMsg, Iv, Key); 78  79         } 80         private static string CreateRandCode(int codeLen) 81         { 82             string codeSerial = "2,3,4,5,6,7,a,c,d,e,f,h,i,j,k,m,n,p,r,s,t,A,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,U,V,W,X,Y,Z"; 83             if (codeLen == 0) 84             { 85                 codeLen = 16; 86             } 87             string[] arr = codeSerial.Split(','); 88             string code = ""; 89             int randValue = -1; 90             Random rand = new Random(unchecked((int)DateTime.Now.Ticks)); 91             for (int i = 0; i < codeLen; i++) 92             { 93                 randValue = rand.Next(0, arr.Length - 1); 94                 code += arr[randValue]; 95             } 96             return code; 97         } 98  99         private static String AES_encrypt(String Input, byte[] Iv, byte[] Key)100         {101             var aes = new RijndaelManaged();102             //秘钥的大小，以位为单位103             aes.KeySize = 256;104             //支持的块大小105             aes.BlockSize = 128;106             //填充模式107             aes.Padding = PaddingMode.PKCS7;108             aes.Mode = CipherMode.CBC;109             aes.Key = Key;110             aes.IV = Iv;111             var encrypt = aes.CreateEncryptor(aes.Key, aes.IV);112             byte[] xBuff = null;113 114             using (var ms = new MemoryStream())115             {116                 using (var cs = new CryptoStream(ms, encrypt, CryptoStreamMode.Write))117                 {118                     byte[] xXml = Encoding.UTF8.GetBytes(Input);119                     cs.Write(xXml, 0, xXml.Length);120                 }121                 xBuff = ms.ToArray();122             }123             String Output = Convert.ToBase64String(xBuff);124             return Output;125         }126 127         private static String AES_encrypt(byte[] Input, byte[] Iv, byte[] Key)128         {129             var aes = new RijndaelManaged();130             //秘钥的大小，以位为单位131             aes.KeySize = 256;132             //支持的块大小133             aes.BlockSize = 128;134             //填充模式135             //aes.Padding = PaddingMode.PKCS7;136             aes.Padding = PaddingMode.None;137             aes.Mode = CipherMode.CBC;138             aes.Key = Key;139             aes.IV = Iv;140             var encrypt = aes.CreateEncryptor(aes.Key, aes.IV);141             byte[] xBuff = null;142 143             #region 自己进行PKCS7补位，用系统自己带的不行144             byte[] msg = new byte[Input.Length + 32 - Input.Length % 32];145             Array.Copy(Input, msg, Input.Length);146             byte[] pad = KCS7Encoder(Input.Length);147             Array.Copy(pad, 0, msg, Input.Length, pad.Length);148             #endregion149 150             #region 注释的也是一种方法，效果一样151             //ICryptoTransform transform = aes.CreateEncryptor();152             //byte[] xBuff = transform.TransformFinalBlock(msg, 0, msg.Length);153             #endregion154 155             using (var ms = new MemoryStream())156             {157                 using (var cs = new CryptoStream(ms, encrypt, CryptoStreamMode.Write))158                 {159                     cs.Write(msg, 0, msg.Length);160                 }161                 xBuff = ms.ToArray();162             }163 164             String Output = Convert.ToBase64String(xBuff);165             return Output;166         }167 168         private static byte[] KCS7Encoder(int text_length)169         {170             int block_size = 32;171             // 计算需要填充的位数172             int amount_to_pad = block_size - (text_length % block_size);173             if (amount_to_pad == 0)174             {175                 amount_to_pad = block_size;176             }177             // 获得补位所用的字符178             char pad_chr = chr(amount_to_pad);179             string tmp = "";180             for (int index = 0; index < amount_to_pad; index++)181             {182                 tmp += pad_chr;183             }184             return Encoding.UTF8.GetBytes(tmp);185         }186         /**187          * 将数字转化成ASCII码对应的字符，用于对明文进行补码188          * 189          * @param a 需要转化的数字190          * @return 转化得到的字符191          */192         static char chr(int a)193         {194 195             byte target = (byte)(a & 0xFF);196             return (char)target;197         }198         private static byte[] AES_decrypt(String Input, byte[] Iv, byte[] Key)199         {200             RijndaelManaged aes = new RijndaelManaged();201             aes.KeySize = 256;202             aes.BlockSize = 128;203             aes.Mode = CipherMode.CBC;204             aes.Padding = PaddingMode.None;205             aes.Key = Key;206             aes.IV = Iv;207             var decrypt = aes.CreateDecryptor(aes.Key, aes.IV);208             byte[] xBuff = null;209             using (var ms = new MemoryStream())210             {211                 using (var cs = new CryptoStream(ms, decrypt, CryptoStreamMode.Write))212                 {213                     byte[] xXml = Convert.FromBase64String(Input);214                     byte[] msg = new byte[xXml.Length + 32 - xXml.Length % 32];215                     Array.Copy(xXml, msg, xXml.Length);216                     cs.Write(xXml, 0, xXml.Length);217                 }218                 xBuff = decode2(ms.ToArray());219             }220             return xBuff;221         }222         private static byte[] decode2(byte[] decrypted)223         {224             int pad = (int)decrypted[decrypted.Length - 1];225             if (pad < 1 || pad > 32)226             {227                 pad = 0;228             }229             byte[] res = new byte[decrypted.Length - pad];230             Array.Copy(decrypted, 0, res, 0, decrypted.Length - pad);231             return res;232         }233     }234 }