如何获取异步Task< string>的返回值；方法名称()? [英] How to get returned value of async Task<string> method name()?

问题描述

我正在尝试获取方法的返回字符串，但是问题是我不知道如何从public async Task<string> Login(string username, string password, string site)获取返回值.

I'm trying to get the return string of my method but the problem is I don't know how can I get the return value from public async Task<string> Login(string username, string password, string site).

这是我来自Program.cs的代码

This is my codes from Program.cs

static void Main(string[] args)
{
    var username = "Leonel.Sarmiento";
    var password = "welcome";
    var site = "QADBSite";
    var url = "na1.sabacloud.com";
    ConsoleCustomizer.Spinner Spinner = new ConsoleCustomizer.Spinner("+", "x", "+", "x");
    ConsoleCustomizer.TypeWriter TypeWriter = new ConsoleCustomizer.TypeWriter(15, 150);
    ConsoleCustomizer.Alerts Alerts = new ConsoleCustomizer.Alerts();
    Alerts.Write("Information", "HOST URL:", null);
    TypeWriter.WriteLine(@"http:\\"+url);
    Alerts.Write("Information", "USERNAME:", null);
    TypeWriter.WriteLine(username);
    Alerts.Write("Information", "PASSWORD:", null);
    for (var i = 0; i < password.Length; i++)
    {
        TypeWriter.Write("*");
    }
    Console.WriteLine("");
    SabaController saba = new SabaController(url);
    //var certificate = saba.Login(username, password, site).Wait();
    saba.Login(username, password, site).Wait();
    Console.Read();
}

这是我来自Saba Controller.cs的代码

This is my codes from Saba Controller.cs

public async Task<string> Login(string username, string password, string site)
{
    using(var client = new HttpClient())
    {
        client.BaseAddress = new Uri("https://" + HostURL + "/");
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.DefaultRequestHeaders.Add("user", username);
        client.DefaultRequestHeaders.Add("password", password);
        client.DefaultRequestHeaders.Add("site", site);
        //HTTP GET: saba/api/login
        HttpResponseMessage response = await client.GetAsync("Saba/api/login");
        if (response.IsSuccessStatusCode)
        {
            SabaModel saba = await response.Content.ReadAsAsync<SabaModel>();
            SabaCertificate = saba.Certificate;
        }
    }
    return SabaCertificate;
}

推荐答案

当前，您只是在调用Wait()-这将阻塞直到任务完成，但不会给您返回值.如果改为使用Result属性，则会阻止该属性，然后为您提供结果:

Currently you're just calling Wait() - that will block until the task completes, but won't give you the return value. If you use the Result property instead, that will block and then give you the result:

string certificate = saba.Login(username, password, site).Result;

现在，它将在 console 应用程序中工作，因为没有SynchronizationContext ...，这意味着async方法的继续将在线程池线程上执行.如果您使用WinForms UI线程中的相同代码(例如)，那么您将陷入死锁-UI线程将等待任务完成，但是直到将任务放到UI上之前，任务无法完成线程来执行更多代码.

Now, that will work in a console app because there's no SynchronizationContext... which means continuations in the async method will be executed on a thread pool thread. If you use the same code from a WinForms UI thread (for example) then you'd end up with a deadlock - the UI thread would be waiting for the task to complete, but the task couldn't complete until it got onto the UI thread to execute some more code.

顺便说一句，这似乎是将SabaCertificate和SabaModel存储在SabaController中，但是应该这样做似乎并不明显.

As an aside, this appears to be storing SabaCertificate and SabaModel in the SabaController, but it's not obvious that it should be doing that.

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