问题
In the code below (a fairly simple one just for demonstration), my finally clause gets executed when awaiting for the HttpClient to finish. So the output is something like:
Done
StatusCode: 200,...
When I was expecting it to be:
StatusCode: 200,...
Done
class Program
{
private static HttpClient _httpClient = new HttpClient();
static async Task Main(string[] args)
{
var numbers = new List<int> {1};
try
{
await Task.Run(() =>
{
Parallel.ForEach(numbers, async (number) => { await Do1(); });
});
}
finally
{
Console.WriteLine("Done");
}
Console.ReadKey();
}
private static async Task Do1()
{
using (var result = await _httpClient.GetAsync("http://www.google.com"))
{
Console.WriteLine(result);
}
}
private static async Task Do2()
{
for (int i = 0; i <= 10; i++)
{
Console.WriteLine("Doing" + await Multiply(i));
}
}
private static async Task<int> Multiply(int number)
{
return await Task.FromResult(number * number);
}
}
If I replace my Main method to use the Do2 method then everything works as expected with the following output ("Done" gets printed at the very end):
.
.
.
Doing100
Done
So why is the HttpClient not working as I am expecting it to work?
Something that I'd like to mention is that I would like to use the Parallel.ForEach instead of the Task.WhenAll function.
来源：https://stackoverflow.com/questions/59412905/parallel-foreach-not-awaiting-for-httpclient