C# 正在检查与HttpClient的Internet连接
我很难理解下面的代码如何处理偶尔的互联网连接丢失。理想情况下,我希望在连接断开后暂停应用程序,然后在再次启动时继续。关于如何做,有什么指导方针吗C# 正在检查与HttpClient的Internet连接,c#,dotnet-httpclient,C#,Dotnet Httpclient,我很难理解下面的代码如何处理偶尔的互联网连接丢失。理想情况下,我希望在连接断开后暂停应用程序,然后在再次启动时继续。关于如何做,有什么指导方针吗 HttpClientHandler clientHandler = new HttpClientHandler(); clientHandler.UseDefaultCredentials = true; HttpClient client = new HttpClient(clientHandler) { MaxResponseContentBuff
HttpClientHandler clientHandler = new HttpClientHandler();
clientHandler.UseDefaultCredentials = true;
HttpClient client = new HttpClient(clientHandler) { MaxResponseContentBufferSize = 1000000 };
HttpResponseMessage response = await client.GetAsync(Url, ct);
下面的示例不是一个直接的解决方案,但它是我创建的一个示例,用于演示如何在脱机时将“预屏蔽”内容返回到请求,然后在恢复连接时返回到联机状态。如果你能得到我在这里所做的,构建你想要的应该是相当容易的
[Fact]
public async Task Getting_a_response_when_offline()
{
var offlineHandler = new OfflineHandler(new HttpClientHandler(), new Uri("http://oak:1001/status"));
offlineHandler.AddOfflineResponse(new Uri("http://oak:1001/ServerNotRunning"),
new HttpResponseMessage(HttpStatusCode.NonAuthoritativeInformation)
{
Content = new StringContent("Here's an old copy of the information while we are offline.")
});
var httpClient = new HttpClient(offlineHandler);
var retry = true;
while (retry)
{
var response = await httpClient.GetAsync(new Uri("http://oak:1001/ServerNotRunning"));
if (response.StatusCode == HttpStatusCode.OK) retry = false;
Thread.Sleep(10000);
}
}
public class OfflineHandler : DelegatingHandler
{
private readonly Uri _statusMonitorUri;
private readonly Dictionary<Uri, HttpResponseMessage> _offlineResponses = new Dictionary<Uri, HttpResponseMessage>();
private bool _isOffline = false;
private Timer _timer;
public OfflineHandler(HttpMessageHandler innerHandler, Uri statusMonitorUri)
{
_statusMonitorUri = statusMonitorUri;
InnerHandler = innerHandler;
}
public void AddOfflineResponse(Uri uri, HttpResponseMessage response)
{
_offlineResponses.Add(uri,response);
}
protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
if (_isOffline == true) return OfflineResponse(request);
try
{
var response = await base.SendAsync(request, cancellationToken);
if (response.StatusCode == HttpStatusCode.ServiceUnavailable || response.StatusCode == HttpStatusCode.BadGateway)
{
MonitorOfflineState();
return OfflineResponse(request);
}
return response;
}
catch (WebException ex)
{
MonitorOfflineState();
return OfflineResponse(request);
}
}
private void MonitorOfflineState()
{
_isOffline = true;
_timer = new Timer( async state =>
{
var request = new HttpRequestMessage() {RequestUri = _statusMonitorUri};
try
{
var response = await base.SendAsync(request, new CancellationToken());
if (response.StatusCode == HttpStatusCode.OK)
{
_isOffline = false;
_timer.Dispose();
}
}
catch
{
}
}, null, new TimeSpan(0,0,0),new TimeSpan(0,1,0));
}
private HttpResponseMessage OfflineResponse(HttpRequestMessage request)
{
if (_offlineResponses.ContainsKey(request.RequestUri))
{
return _offlineResponses[request.RequestUri];
}
return new HttpResponseMessage(HttpStatusCode.ServiceUnavailable);
}
}
}
[事实]
公共异步任务在脱机时获取响应()
{
var offlineHandler=新的offlineHandler(新的HttpClientHandler(),新的Uri(“http://oak:1001/status"));
offlineHandler.AddOfflineResponse(新Uri(“http://oak:1001/ServerNotRunning"),
新的HttpResponseMessage(HttpStatusCode.非授权信息)
{
Content=new-StringContent(“这是我们脱机时信息的旧副本。”)
});
var httpClient=新的httpClient(离线处理程序);
var retry=true;
while(重试)
{
var response=wait httpClient.GetAsync(新Uri(“http://oak:1001/ServerNotRunning"));
如果(response.StatusCode==HttpStatusCode.OK)retry=false;
睡眠(10000);
}
}
公共类脱机处理程序:DelegatingHandler
{
私有只读Uri _statusMonitorUri;
专用只读词典_offlineResponses=新词典();
private bool_Isofline=假;
私人定时器;
公共脱机处理程序(HttpMessageHandler innerHandler,Uri statusMonitorUri)
{
_statusMonitorUri=statusMonitorUri;
InnerHandler=InnerHandler;
}
public void AddOfflineResponse(Uri、HttpResponseMessage响应)
{
_添加(uri,响应);
}
受保护的异步覆盖任务SendAsync(HttpRequestMessage请求,CancellationToken CancellationToken)
{
如果(_isOffline==true)返回脱机响应(请求);
尝试
{
var response=await base.sendaync(请求、取消令牌);
if(response.StatusCode==HttpStatusCode.serviceinavailable | | response.StatusCode==HttpStatusCode.BadGateway)
{
监视器脱机状态();
返回离线响应(请求);
}
返回响应;
}
捕获(WebException ex)
{
监视器脱机状态();
返回离线响应(请求);
}
}
私有void监视器脱机状态()
{
_异弗林=真;
_计时器=新计时器(异步状态=>
{
var request=new-HttpRequestMessage(){RequestUri=\u statusMonitorUri};
尝试
{
var response=await base.sendaync(请求,new CancellationToken());
if(response.StatusCode==HttpStatusCode.OK)
{
_异黄酮=假;
_timer.Dispose();
}
}
抓住
{
}
},null,新时间跨度(0,0,0),新时间跨度(0,1,0));
}
专用HttpResponseMessageOfflineResponse(HttpRequestMessage请求)
{
if(_offlineResponses.ContainsKey(request.RequestUri))
{
返回_offlineResponses[request.RequestUri];
}
返回新的HttpResponseMessage(HttpStatusCode.ServiceUnavailable);
}
}
}