C# 后台发送http请求

 public class WllRequest
 {
     private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
     {
          return true; //总是接受  
     }
     
    public static string HttpRequest(string url)
    {
        try
        {
            HttpWebRequest httpRequest;
            if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
            {
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                httpRequest = WebRequest.Create(url) as HttpWebRequest;
                httpRequest.ProtocolVersion = HttpVersion.Version10;
            }
            else
                httpRequest = WebRequest.Create(url) as HttpWebRequest;
            httpRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36";
            HttpWebResponse httpResp = (HttpWebResponse)httpRequest.GetResponse();
            Stream responseStream = httpResp.GetResponseStream(); //获得响应的流
            StringBuilder strBuff = new StringBuilder();
            using (StreamReader responseStreamReader = new StreamReader(responseStream, Encoding.UTF8))
            {
                char[] cbuffer = new char[256];
                int byteRead = responseStreamReader.Read(cbuffer, 0, 256);
                while (byteRead != 0)
                {
                    string strResp = new string(cbuffer, 0, byteRead);
                    strBuff.Append(strResp);
                    byteRead = responseStreamReader.Read(cbuffer, 0, 256);
                }
            }
            return strBuff.ToString();
        }
        catch(Exception ex)
        {
            //如何需要记录错误日志可在这里记录 或抛出异常
            return null;
        }
    }

    /// <summary>
    /// Post请求
    /// </summary>
    /// <param name="url">请求的地址</param>
    /// <param name="ua">用户代理</param>
    /// <param name="param">请求的参数 => json字符串</param>
    /// <returns>返回json字符串</returns>
    public static string Post(string url,string ua, string param)
    {
    try{
        HttpWebRequest httpRequest;
        if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
        {
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
            httpRequest = WebRequest.Create(url) as HttpWebRequest;
            httpRequest.ProtocolVersion = HttpVersion.Version10;
        }
        else
            httpRequest = WebRequest.Create(url) as HttpWebRequest;
        httpRequest.UserAgent = ua;
        httpRequest.Method = "POST";
        httpRequest.ContentType = "application/json;charset=UTF-8";
        string paraUrlCoded = param;
        byte[] payload = System.Text.Encoding.UTF8.GetBytes(paraUrlCoded);
        httpRequest.ContentLength = payload.Length;
        using (Stream wStream = httpRequest.GetRequestStream())
        {
            wStream.Write(payload, 0, payload.Length);
        }
        HttpWebResponse response = (System.Net.HttpWebResponse)httpRequest.GetResponse();
        Stream responseStream = response.GetResponseStream();
        StringBuilder strBuff = new StringBuilder();
        using (StreamReader responseStreamReader = new StreamReader(responseStream, Encoding.UTF8))
        {
            char[] cbuffer = new char[256];
            int byteRead = responseStreamReader.Read(cbuffer, 0, 256);
            while (byteRead != 0)
            {
                string strResp = new string(cbuffer, 0, byteRead);
                strBuff.Append(strResp);
                byteRead = responseStreamReader.Read(cbuffer, 0, 256);
            }
        }
        return strBuff.ToString();
        }
        catch(Exception ex){
             //如何需要记录错误日志可在这里记录 或抛出异常
             return null;
        }
    }

    /// <summary>
    /// GET请求
    /// </summary>
    /// <param name="url">请求的地址</param>
    /// <param name="ua">用户代理</param>
    /// <param name="param">请求的参数 => json字符串</param>
    /// <returns>返回json字符串</returns>
    public static string Get(string url, string ua, string param)
    {
    try{
        HttpWebRequest httpRequest;
        if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
        {
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
            httpRequest = WebRequest.Create(url) as HttpWebRequest;
            httpRequest.ProtocolVersion = HttpVersion.Version10;
        }
        else
            httpRequest = WebRequest.Create(url) as HttpWebRequest;
        httpRequest.UserAgent = ua;
        httpRequest.ContentType = "application/json;charset=UTF-8";
        string paraUrlCoded = param;
        byte[] payload = System.Text.Encoding.UTF8.GetBytes(paraUrlCoded);
        httpRequest.ContentLength = payload.Length;
        using (Stream wStream = httpRequest.GetRequestStream())
        {
            wStream.Write(payload, 0, payload.Length);
        }
        HttpWebResponse response = (System.Net.HttpWebResponse)httpRequest.GetResponse();
        Stream responseStream = response.GetResponseStream();
        StringBuilder strBuff = new StringBuilder();
        using (StreamReader responseStreamReader = new StreamReader(responseStream, Encoding.UTF8))
        {
            char[] cbuffer = new char[256];
            int byteRead = responseStreamReader.Read(cbuffer, 0, 256);
            while (byteRead != 0)
            {
                string strResp = new string(cbuffer, 0, byteRead);
                strBuff.Append(strResp);
                byteRead = responseStreamReader.Read(cbuffer, 0, 256);
            }
        }
        return strBuff.ToString();
        }
        catch(Exception ex){
              //如何需要记录错误日志可在这里记录 或抛出异常
             return null;
        }
    }
}
<think>好的,我需要帮助用户在C#后台实现发送和监听请求的功能。首先,我得明确用户的需求。他们可能想在后端服务中既能发送HTTP请求到外部API,又能监听传入的请求,比如作为WebAPI服务器。接下来,我要考虑常见的实现方式。 发送请求方面,C#常用的有HttpClient类,它支持异步操作,适合高性能场景。需要提醒用户注意使用单例模式,避免端口耗尽。同时,处理异常和配置超时也是关键点。这部分需要示例代码,展示GET和POST请求的基本用法。监听请求的话,有几种选择。如果是ASP.NETCore应用,可以使用内置的Kestrel服务器,通过控制器处理路由。对于更简单的需求,可能用HttpListener类,它基于Http.sys驱动,适合小型服务。这里需要比较两者的优缺点,帮助用户根据项目规模选择。比如,ASP.NETCore适合完整的Web API,而HttpListener适合轻量级监听。 用户可能还会关心异步处理、路由配置、中间件等方面。比如,如何在监听时解析请求参数,或者添加日志中间件。需要提供相关代码示例,比如使用HttpListener的异步上下文处理,或者ASP.NET Core的控制器结构。 另外,性能优化和错误处理也是重点。比如,使用缓冲区和连接池提升发送效率,处理网络异常和超时。对于监听部分,配置合适的缓冲区大小和并发处理,避免阻塞。最后,生成相关问题,帮助用户深入理解。比如,如何提高并发处理能力,或者选择HTTP客户端的不同方法比较。确保问题覆盖用户可能遇到的进阶挑战,引导他们进一步学习。</think>### 如何在C#后台实现发送和监听请求的功能 #### 1. **发送HTTP请求** 在C#发送HTTP请求主要通过`HttpClient`类实现。以下是关键步骤和示例: ##### 1.1 基本GET/POST请求 ```csharp // 推荐使用单例HttpClient以避免端口耗尽 private static readonly HttpClient _httpClient = new HttpClient(); public async Task<string> SendGetRequest(string url) { try { var response = await _httpClient.GetAsync(url); response.EnsureSuccessStatusCode(); return await response.Content.ReadAsStringAsync(); } catch (HttpRequestException ex) { // 处理网络错误 } } public async Task<string> SendPostRequest(string url, string jsonData) { var content = new StringContent(jsonData, Encoding.UTF8, "application/json"); var response = await _httpClient.PostAsync(url, content); return await response.Content.ReadAsStringAsync(); } ``` ##### 1.2 高级配置 - **超时控制**:`_httpClient.Timeout = TimeSpan.FromSeconds(30);` - **请求头定制**:`_httpClient.DefaultRequestHeaders.Add("User-Agent", "C#Backend");` - **连接池优化**:通过`SocketsHttpHandler`配置连接生命周期[^1] #### 2. **监听HTTP请求** 实现监听有两种主流方案: ##### 2.1 方案一:ASP.NET Core Web API(推荐) ```csharp // Program.cs var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); var app = builder.Build(); app.MapControllers(); app.Run(); // Controller示例 [ApiController] [Route("api/[controller]")] public class DataController : ControllerBase { [HttpGet("status")] public IActionResult GetStatus() { return Ok(new { Status = "Active" }); } [HttpPost("upload")] public async Task<IActionResult> UploadData([FromBody] dynamic data) { // 处理数据 return CreatedAtAction(nameof(GetStatus), new { id = 1 }); } } ``` 特点: - 内置依赖注入 - 支持中间件管道(日志、鉴权等) - 自动路由参数解析 ##### 2.2 方案二:HttpListener(轻量级) ```csharp using var listener = new HttpListener(); listener.Prefixes.Add("http://localhost:8080/"); listener.Start(); while (true) { var context = await listener.GetContextAsync(); _ = ProcessRequestAsync(context); // 异步处理 } async Task ProcessRequestAsync(HttpListenerContext ctx) { var request = ctx.Request; var response = ctx.Response; try { switch (request.Url?.AbsolutePath) { case "/api/data": var body = await new StreamReader(request.InputStream).ReadToEndAsync(); // 处理逻辑 await response.OutputStream.WriteAsync(Encoding.UTF8.GetBytes("OK")); break; default: response.StatusCode = 404; break; } } finally { response.Close(); } } ``` 特点: - 无需依赖Web框架 - 需要手动处理路由、参数解析 - 适合简单监控端口 #### 3. **关键优化点** - **并发处理**:使用`async/await`避免阻塞线程 - **错误恢复**: ```csharp // HttpClient重试策略 var retryPolicy = Policy.Handle<HttpRequestException>() .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))); ``` - **性能监控**:通过`System.Diagnostics.Metrics`记录QPS、延迟等指标 - **缓冲区管理**:使用`ArrayPool<byte>`减少内存分配 #### 4. **WebSocket实现** 对于双向通信需求: ```csharp // ASP.NET Core中的WebSocket app.UseWebSockets(); app.Use(async (context, next) => { if (context.WebSockets.IsWebSocketRequest) { using var webSocket = await context.WebSockets.AcceptWebSocketAsync(); await EchoWebSocket(webSocket); } else await next(); }); async Task EchoWebSocket(WebSocket webSocket) { var buffer = new byte[1024]; while (webSocket.State == WebSocketState.Open) { var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None); await webSocket.SendAsync(buffer[..result.Count], WebSocketMessageType.Text, result.EndOfMessage, CancellationToken.None); } } ```
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