用C#实现微信聊天功能

实现微信聊天功能需要使用微信开发者工具和微信公众平台开发接口进行开发。以下是一个简单的实现微信聊天功能的C#代码示例：

using System;
using System.Net;
using System.IO;
using System.Text;
using System.Web.Script.Serialization;

namespace WeChatChat
{
    class Program
    {
        static void Main(string[] args)
        {
            // 设置微信公众平台的参数
            string appId = "your_app_id";
            string appSecret = "your_app_secret";
            string token = "your_token";
            string encodingAESKey = "your_encoding_aes_key";

            // 获取微信服务器发送的消息
            string postStr = GetPostStr();
            if (!string.IsNullOrEmpty(postStr))
            {
                // 对消息进行解密
                string decryptStr = WeChatEncrypt.AESDecrypt(postStr, encodingAESKey, appId);
                if (!string.IsNullOrEmpty(decryptStr))
                {
                    // 解析消息内容
                    JavaScriptSerializer serializer = new JavaScriptSerializer();
                    Message message = serializer.Deserialize<Message>(decryptStr);

                    // 处理消息
                    if (message.MsgType == "text")
                    {
                        // 回复消息
                        string content = "您发送的消息是：" + message.Content;
                        string response = WeChatEncrypt.AESEncrypt(WeChatResponse.TextResponse(message.FromUserName, message.ToUserName, content), encodingAESKey, appId);
                        Console.WriteLine(response);
                    }
                }
            }
        }

        // 获取微信服务器发送的消息
        private static string GetPostStr()
        {
            Stream inputStream = Console.OpenStandardInput();
            byte[] bytes = new byte[1024];
            int length = inputStream.Read(bytes, 0, 1024);
            return Encoding.UTF8.GetString(bytes, 0, length);
        }
    }

    // 微信消息类
    public class Message
    {
        public string ToUserName { get; set; }
        public string FromUserName { get; set; }
        public long CreateTime { get; set; }
        public string MsgType { get; set; }
        public string Content { get; set; }
        public string MsgId { get; set; }
    }

    // 微信消息响应类
    public class WeChatResponse
    {
        public static string TextResponse(string toUserName, string fromUserName, string content)
        {
            string response = string.Format(@"<xml>
                                                <ToUserName><![CDATA[{0}]]></ToUserName>
                                                <FromUserName><![CDATA[{1}]]></FromUserName>
                                                <CreateTime>{2}</CreateTime>
                                                <MsgType><![CDATA[text]]></MsgType>
                                                <Content><![CDATA[{3}]]></Content>
                                            </xml>", toUserName, fromUserName, DateTime.Now.Ticks, content);
            return response;
        }
    }

    // 微信加解密类
    public class WeChatEncrypt
    {
        public static string AESEncrypt(string content, string encodingAESKey, string appId)
        {
            byte[] key = Convert.FromBase64String(encodingAESKey + "=");
            byte[] iv = new byte[16];
            Array.Copy(key, iv, 16);
            byte[] data = Encoding.UTF8.GetBytes(content);
            byte[] pad = PKCS7Padding(data);
            byte[] encrypted = null;
            using (var aes = new System.Security.Cryptography.AesCryptoServiceProvider())
            {
                aes.KeySize = 256;
                aes.BlockSize = 128;
                aes.Key = key;
                aes.IV = iv;
                aes.Mode = System.Security.Cryptography.CipherMode.CBC;
                aes.Padding = System.Security.Cryptography.PaddingMode.None;
                using (var encryptor = aes.CreateEncryptor())
                {
                    encrypted = encryptor.TransformFinalBlock(pad, 0, pad.Length);
                }
            }
            string base64 = Convert.ToBase64String(encrypted);
            string nonce = Guid.NewGuid().ToString().Replace("-", "");
            string timestamp = DateTime.Now.Ticks.ToString().Substring(0, 10);
            string signature = SHA1($"{token}\n{timestamp}\n{nonce}\n{base64}");
            string response = string.Format(@"<xml>
                                                <Encrypt><![CDATA[{0}]]></Encrypt>
                                                <MsgSignature><![CDATA[{1}]]></MsgSignature>
                                                <TimeStamp>{2}</TimeStamp>
                                                <Nonce><![CDATA[{3}]]></Nonce>
                                            </xml>", base64, signature, timestamp, nonce);
            return response;
        }

        public static string AESDecrypt(string content, string encodingAESKey, string appId)
        {
            byte[] key = Convert.FromBase64String(encodingAESKey + "=");
            byte[] iv = new byte[16];
            Array.Copy(key, iv, 16);
            string[] arr = content.Split('\n');
            string base64 = arr[1].Replace("<Encrypt><![CDATA[", "").Replace("]]></Encrypt>", "");
            string signature = arr[2].Replace("<MsgSignature><![CDATA[", "").Replace("]]></MsgSignature>", "");
            string timestamp = arr[3].Replace("<TimeStamp>", "").Replace("</TimeStamp>", "");
            string nonce = arr[4].Replace("<Nonce><![CDATA[", "").Replace("]]></Nonce>", "");
            string plainText = null;
            try
            {
                byte[] encrypted = Convert.FromBase64String(base64);
                using (var aes = new System.Security.Cryptography.AesCryptoServiceProvider())
                {
                    aes.KeySize = 256;
                    aes.BlockSize = 128;
                    aes.Key = key;
                    aes.IV = iv;
                    aes.Mode = System.Security.Cryptography.CipherMode.CBC;
                    aes.Padding = System.Security.Cryptography.PaddingMode.None;
                    using (var decryptor = aes.CreateDecryptor())
                    {
                        byte[] decrypted = decryptor.TransformFinalBlock(encrypted, 0, encrypted.Length);
                        plainText = Encoding.UTF8.GetString(PKCS7Unpadding(decrypted));
                    }
                }
            }
            catch
            {
                return null;
            }
            string hash = SHA1($"{token}\n{timestamp}\n{nonce}\n{plainText}");
            if (hash == signature)
            {
                return plainText;
            }
            else
            {
                return null;
            }
        }

        private static byte[] PKCS7Padding(byte[] data)
        {
            int length = data.Length;
            int pad = 32 - length % 32;
            byte[] padding = new byte[pad];
            for (int i = 0; i < pad; i++)
            {
                padding[i] = (byte)pad;
            }
            byte[] result = new byte[length + pad];
            Array.Copy(data, result, length);
            Array.Copy(padding, 0, result, length, pad);
            return result;
        }

        private static byte[] PKCS7Unpadding(byte[] data)
        {
            int length = data.Length;
            int pad = (int)data[length - 1];
            byte[] result = new byte[length - pad];
            Array.Copy(data, result, length - pad);
            return result;
        }

        private static string SHA1(string data)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(data);
            using (var sha1 = System.Security.Cryptography.SHA1.Create())
            {
                byte[] hash = sha1.ComputeHash(bytes);
                return BitConverter.ToString(hash).Replace("-", "").ToLower();
            }
        }
    }
}

上述代码中使用了微信加解密算法进行消息的加解密，同时使用了微信消息响应类进行消息的回复。需要注意的是，该代码只是一个简单的示例，实际开发中需要根据需求进行更详细的开发。同时，微信公众平台开发需要符合微信的开发规范和要求，需要进行相关的认证和申请，开发前需要进行充分了解和准备。