c# - 在 asp.net 中等待 GetByteArrayAsync 不返回

Question

以下代码在从 ASP.NET 应用程序调用时挂起:

private async Task<XPathNavigator> UspsCreateAndPostRequest(string sUrl)
{
  HttpClient client = new HttpClient();
  byte[] urlContents = await client.GetByteArrayAsync(sUrl);
  string sResponse = System.Text.Encoding.UTF8.GetString(urlContents);
  ... //more code to return XPathNavigator object based on response
}

如果我改成跟随它就可以正常工作:

private async Task<XPathNavigator> UspsCreateAndPostRequest(string sUrl)
{
  HttpClient client = new HttpClient();
  byte[] urlContents = null;
  var task = Task.Run(async () => { urlContents = await client.GetByteArrayAsync(strUrl); });
  task.Wait();
  string sResponse = System.Text.Encoding.UTF8.GetString(urlContents);
  ... //more code to return XPathNavigator object based on response
}

方法签名返回是一个 Task 是否导致了这个问题？谢谢。

Answer 1

在调用堆栈的较高位置，有一个 .Wait() 正在对从 UspsCreateAndPostRequest 返回的任务执行。

因为您将调用包装在 Task.Run 中，所以您丢失了执行上下文，这就是它起作用的原因。做

private async Task<XPathNavigator> UspsCreateAndPostRequest(string sUrl)
{
  HttpClient client = new HttpClient();
  byte[] urlContents = await client.GetByteArrayAsync(sUrl).ConfigureAwait(false);
  string sResponse = System.Text.Encoding.UTF8.GetString(urlContents);
  ... //more code to return XPathNavigator object based on response
}

可以用更少的资源实现相同的目标(但将等待修复在链上更高的位置会更好)。