Question

我正在尝试使用HttpClient从REST API获取数据，但是我遇到了问题。使用相同的服务，但通过控制台应用程序，一切正常。

在Controller上一切正常，但是在调用HttpHandler的GetAsync（url）方法时，似乎在后台执行了某些操作，但是什么也没有发生。

这是我的服务

public class UserService : IUsersService
{
    private const string url = "https://jsonplaceholder.typicode.com/users";
    private IHttpHandler httpHandler;

    public UserService(IHttpHandler httpHandler)
    {
        this.httpHandler = httpHandler;
    }

    public List<User> GetAllUsers()
    {
        HttpResponseMessage response = httpHandler.Get(url);

        if (response.IsSuccessStatusCode)
        {
            return response.Content.ReadAsAsync<List<User>>().Result;
        }

        //Nice to add Logging system that we cannot connect into following URL
        return new List<User>();
    }

    public User GetUserById(int userId)
    {
        HttpResponseMessage response = httpHandler.Get(
            string.Concat(url,"?id=",userId));

        if (response.IsSuccessStatusCode)
        {
            return response.Content.ReadAsAsync<List<User>>().Result.FirstOrDefault();
        }

        //Nice to add Logging system that we cannot connect into following URL
        return null;
    }
}

这是我的控制器（使用WEB API控制器，httpClient无法从REST API获取数据）

public class UsersController : ApiController
{
    IUsersService userService;

    public UsersController(IUsersService userService)
    {
        this.userService = userService;
    }

    public List<User> GetUsers()
    {
        return userService.GetAllUsers();
    }

    public User GetUser(int userId)
    {
        return userService.GetUserById(userId);
    }
}

这是我的HttpHandler，当前正在使用HttpClient：

public class HttpHandler : IHttpHandler
{
    private HttpClient client = new HttpClient();

    public HttpResponseMessage Get(string url)
    {
        return GetAsync(url).Result;
    }

    public HttpResponseMessage Post(string url, HttpContent content)
    {
        return PostAsync(url, content).Result;
    }

    public async Task<HttpResponseMessage> GetAsync(string url)
    {
        return await client.GetAsync(url);
    }

    public async Task<HttpResponseMessage> PostAsync(string url, HttpContent content)
    {
        return await client.PostAsync(url, content);
    }
}

这是我的控制台应用程序，可以正常运行并显示正确的结果：

class Program
{
    static void Main(string[] args)
    {
        HttpHandler handler = new HttpHandler();
        UserService service = new UserService(handler);

        var users = service.GetAllUsers();

        Console.WriteLine(users[0].Email);
        Console.ReadKey();
    }
}

我真的不知道，可能是个问题。

Answer 1

在挖掘网络期间，我找到了问题https://stackoverflow.com/a/10369275/5002910

的解决方案

在GetAsync方法的HttpHandler类中，我必须返回 return await client.GetAsync(url).ConfigureAwait(continueOnCapturedContext:false);

使用.NET Core从REST API获取数据

1 个答案: