c# - ASP.NET MVC API 库

Question

使用类库从 Web API 获取数据并在同一解决方案的 MVC 项目中引用它。

在浏览器中加载索引页面时不断出现错误，提示我需要用 <%@ Page Async="true" %> 标记页面或返回任务。但是 Controller 方法不允许我使用 public async Task MakeCall(string url)说找不到类型或命名空间任务。

库类:

public class GetObject
{
    public async Task GetRequest(string url)
    {
        using (HttpClient client = new HttpClient())
        using (HttpResponseMessage response = await client.GetAsync(url))
        using (HttpContent content = response.Content)
        {
            string data = await content.ReadAsStringAsync();
            HttpContentHeaders headers = content.Headers;
        }
    }
}

在我使用的 Controller 中:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        MakeCall("http://api.openweathermap.org/data/2.5/weather?q=London&APPID=[APIKEY]");
        return View();
    }

    public async void MakeCall(string url)
    {
        GetObject newCall = new GetObject();
        await newCall.GetRequest(url);
    }
}

Answer 1

避免 async void 触发后遗忘方法。通过确保包含必要的命名空间(例如 using System.Threading.Tasks;

)使代码始终异步

例如

//...other using
using System.Threading.Tasks;

public class HomeController : Controller {
    public async Task<ActionResult> Index() {
        await MakeCall("http://api.openweathermap.org/data/2.5/weather?q=London&APPID=[APIKEY]");
        return View();
    }

    public async Task MakeCall(string url) {
        GetObject newCall = new GetObject();
        await newCall.GetRequest(url);

    }
}