我将为您翻译以下内容：
在Windows上创建.NET Core 3.1控制台应用程序时，我试图弄清楚为什么使用HttpCompletionOption.ResponseHeadersRead后获取内容时，httpClient.Timeout似乎不起作用。
static async Task Main(string[] args)
{
var httpClient = new HttpClient();
// if using HttpCompletionOption this timeout doesn't work
httpClient.Timeout = TimeSpan.FromSeconds(5);
var uri = new Uri("http://brokenlinkcheckerchecker.com/files/200MB.zip");
// will not timeout
//using var httpResponseMessage = await httpClient.GetAsync(uri, HttpCompletionOption.ResponseHeadersRead);
// will timeout after 5s with a TaskCanceledException
var httpResponseMessage = await httpClient.GetAsync(uri);
Console.WriteLine($"Status code is {httpResponseMessage.StatusCode}. Press any key to get content");
Console.ReadLine();
Console.WriteLine("getting content");
var html = await httpResponseMessage.Content.ReadAsStringAsync();
Console.WriteLine($"finished and length is {html.Length}");
}
我也尝试过使用 CancellationToken
// will not timeout
var cts = new CancellationTokenSource(5000);
using var httpResponseMessage = await httpClient.GetAsync(uri, HttpCompletionOption.ResponseHeadersRead,
cts.Token);
以及 ReadAsStreamAsync
// will not timeout
using (Stream streamToReadFrom = await httpResponseMessage.Content.ReadAsStreamAsync())
{
string fileToWriteTo = Path.GetTempFileName();
using (Stream streamToWriteTo = File.Open(fileToWriteTo, FileMode.Create))
{
await streamToReadFrom.CopyToAsync(streamToWriteTo);
}
}
我从这篇优秀的文章中学到了关于HttpCompletionOption的内容:
https://www.stevejgordon.co.uk/using-httpcompletionoption-responseheadersread-to-improve-httpclient-performance-dotnet
更新
通过使用@StephenCleary的答案，将cancellationToken传递给CopyToAsync方法，现在已按预期工作。
下面是更新后的代码，它展示了如何将数据复制到MemoryStream，然后再复制到字符串中。我发现这很棘手。对于我的用例来说，这很好用。
string html;
await using (var streamToReadFrom = await httpResponseMessage.Content.ReadAsStreamAsync())
await using (var streamToWriteTo = new MemoryStream())
{
await streamToReadFrom.CopyToAsync(streamToWriteTo, cts.Token);
// careful of what encoding - read from incoming MIME
html = Encoding.UTF8.GetString(streamToWriteTo.ToArray());
}