c# - 检索在 Task.WhenAll 抛出异常时起作用的内容

Question

考虑

string[] pages;
Task [] asyncOps = 
    (from url in urls select DownloadStringAsync(url)).ToArray();
try
{
    pages = await Task.WhenAll(asyncOps);
    ...
}
catch(Exception exc)
{
    foreach(Task<string> faulted in asyncOps.Where(t => t.IsFaulted))
    {
        … // work with faulted and faulted.Exception
    }
}

来自 https://msdn.microsoft.com/en-us/library/hh873173%28v=vs.110%29.aspx .如何检索 DID 有效的页面？

或者更好的是，我怎样才能继续计算其余页面？

Answer 1

与其进行所有下载然后分别处理每个成功/错误，我认为如果您定义一个单独的“下载并处理错误”操作会更简洁:

Task [] asyncOps = 
    (from url in urls select DownloadStringWithErrorCheckingAsync(url)).ToArray();
string[] pages = await Task.WhenAll(asyncOps);
var successfulPages = pages.Where(x => x != null);

...

private static Task<string> DownloadStringWithErrorCheckingAsync(string url)
{
  try
  {
    return await DownloadStringAsync(url);
  }
  catch(Exception exc)
  {
    ... // work with exc
    return null;
  }
}