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所属分类：.NET技术
当使用c# HttpClient 发送请求时，由于网络等原因可能会出现超时的情况。为了提高请求的成功率，我们可以使用超时重试的机制。
超时重试的实现方式可以使用循环结构，在请求发起后等待一定时间，若超时未收到响应，则再次发起请求。循环次数可以根据实际情况进行设置，一般建议不超过三次。
百度搜索的关于c#HttpClient 的比较少，简单整理了下，代码如下
//调用方式 3秒后超时 重试2次 .net framework 4.5 HttpMessageHandler handler = new TimeoutHandler(2,3000); using (var client = new HttpClient(handler)) { using (var content = new StringContent(""), null, "application/json")) { var response = client.PostAsync("url", content).Result; string result = response.Content.ReadAsStringAsync().Result; JObject jobj = JObject.Parse(result); if (jobj.Value<int>("code") == 1) { } } }
public class TimeoutHandler : DelegatingHandler { private int _timeout; private int _max_count; /// /// 超时重试 /// ///重试次数 ///超时时间 public TimeoutHandler( int max_count = 3, int timeout = 5000) { base .InnerHandler = new HttpClientHandler(); _timeout = timeout; _max_count = max_count; } protected async override Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { HttpResponseMessage response = null ; for ( int i = 1; i <= _max_count + 1; i++) { var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken); cts.CancelAfter(_timeout); try { response = await base .SendAsync(request, cts.Token); if (response.IsSuccessStatusCode) { return response; } } catch (Exception ex) { //请求超时 if (ex is TaskCanceledException) { MyLogService.Print( "接口请求超时：" + ex.ToString()); if (i > _max_count) { return new HttpResponseMessage(HttpStatusCode.OK) { Content = new StringContent( "{"code":-1,"data":"","msg":"接口请求超时"}" , Encoding.UTF8, "text/json" ) }; } MyLogService.Print($ "接口第{i}次重新请求" ); } else { MyLogService.Error( "接口请求出错：" + ex.ToString()); return new HttpResponseMessage(HttpStatusCode.OK) { Content = new StringContent( "{"code":-1,"data":"","msg":"接口请求出错"}" , Encoding.UTF8, "text/json" ) }; } } } return response; } }
