HttpClient 完成后如何处理？

Question

I want to use HttpClient to get content for my web page.

public async Task<IActionResult> OnGet()
{
    NetworkCredential credentials = new NetworkCredential(Settings.Username, Settings.Password);

    using (HttpClientHandler handler = new HttpClientHandler { Credentials = credentials })
    using (HttpClient httpClient = new HttpClient(handler))
    {
        Content = await httpClient.GetStringAsync(requestUriString);
    }

    return Page();
}

The problem is that my using statements cause the HttpClient and HttpClientHandler objects to be destroyed before GetStringAsync() has completed.

I can remove the using statements, but then I can't be assured the connections get disposed in a timely fashion.

Note that HttpClient does not implement IAsyncDisposable and so using await using is not an option.

How can I ensure my HTTP objects get disposed of as soon as possible without disposing them before the code is finished?

Answer 1

So HttpClient is actually a bit weird in the context of being an IDisposable. Even though it implements the IDisposable interface, Microsoft actually advises against placing it in a using statement .

If you are using it in an ASP.NET Core context, you should use the HttpClientFactory to manage the lifetime of your HttpClients. If not, it is recommended to use a single static instance, but be wary that this can cause other issues, such as DNS staleness.

Answer 2

I found this article helpful when I had a similar issue: https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/ Here's an excerpt of the code you're looking for:

private static HttpClient Client = new HttpClient();
public static async Task Main(string[] args) 
{
    Console.WriteLine("Starting connections");
    for(int i = 0; i<10; i++)
    {
        var result = await Client.GetAsync("http://aspnetmonsters.com");
        Console.WriteLine(result.StatusCode);
    }
    Console.WriteLine("Connections done");
    Console.ReadLine();
}