在页面构造函数中异步调用 Web 服务 [英] Calling web service asynchronously in page constructor
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问题描述
我需要在 Windows 10 UWP 应用程序的 XAML 页面上加载数据.为此,我编写了代码以在异步任务函数中调用 Web 服务,并在页面构造函数中调用它.你能告诉最好的方法吗?以下是我的代码.
I need to load data on a XAML page in a windows 10 UWP application. For that I wrote code to call the web service in async task function, and I call this in page constructor. Could you please tell best way to do this? Following is my code.
public sealed partial class MyDownloads : Page
{
string result;
public MyDownloads()
{
this.InitializeComponent();
GetDownloads().Wait();
string jsonstring = result;
//code for binding follows
}
private async Task GetDownloads()
{
JsonObject jsonObject = new JsonObject
{
{"StudentID", JsonValue.CreateStringValue(user.Student_Id.ToString()) },
};
string ServiceURI = "http://m.xxx.com/xxxx.svc/GetDownloadedNotes";
HttpClient httpClient = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, ServiceURI);
request.Content = new StringContent(jsonObject.ToString(), Encoding.UTF8, "application/json");
HttpResponseMessage response = await httpClient.SendAsync(request);
string returnString = await response.Content.ReadAsStringAsync();
result = returnString;
}
}
推荐答案
相反,您需要使用 OnNavigatedTo
因为,GetDownloads().Wait()
不好的做法.你阻塞 UI 线程直到执行结束
because, GetDownloads().Wait()
bad practice. You block UI Thread until the end of execution
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
}
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
var result = await GetDownloadsAsync();
string jsonstring = result;
}
private async Task<string> GetDownloadsAsync()
{
JsonObject jsonObject = new JsonObject
{
{"StudentID", JsonValue.CreateStringValue(user.Student_Id.ToString()) },
};
string ServiceURI = "http://m.xxx.com/xxxx.svc/GetDownloadedNotes";
HttpClient httpClient = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, ServiceURI);
request.Content = new StringContent(jsonObject.ToString(), Encoding.UTF8, "application/json");
HttpResponseMessage response = await httpClient.SendAsync(request);
string returnString = await response.Content.ReadAsStringAsync();
return returnString;
}
}
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