如何使普通的 WebRequest 异步和等待? [英] How to make ordinary WebRequest async and awaitable?
问题描述
我需要使以下代码异步且可等待.
I need to make the following code async and awaitable.
我需要从 Web 服务器获取大量数据,然后这些数据将用于填充我的应用程序中的 xaml 页面.
I need to get a lot of data from the web server, and then this data will be used to populate the xaml page in my application.
所以,我需要 DefLogin() 方法可以等待.
So, I need the DefLogin() method to be awaitable.
有可能吗?
public void DefLogin()
{
postData = "My Data To Post";
var url = new Uri("Url To Post to", UriKind.Absolute);
webRequest = WebRequest.Create(url);
webRequest.Method = "POST";
webRequest.ContentType = "text/xml";
webRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), webRequest);
}
public void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
webRequest = (HttpWebRequest)asynchronousResult.AsyncState;
Stream postStream = webRequest.EndGetRequestStream(asynchronousResult);
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
Debug.WriteLine("Start BEGINGetResponse");
webRequest.BeginGetResponse(new AsyncCallback(GetResponseCallback), webRequest);
}
public void GetResponseCallback(IAsyncResult asynchronousResult)
{
try
{
HttpWebRequest webRequest = (HttpWebRequest)asynchronousResult.AsyncState;
HttpWebResponse response;
response = (HttpWebResponse)webRequest.EndGetResponse(asynchronousResult);
Stream streamResponse = response.GetResponseStream();
StreamReader streamReader = new StreamReader(streamResponse);
string Response = streamReader.ReadToEnd();
streamResponse.Close();
streamReader.Close();
response.Close();
if (Response == "")
{
//show some error msg to the user
Debug.WriteLine("ERROR");
}
else
{
//Your response will be available in "Response"
Debug.WriteLine(Response);
}
}
catch (WebException)
{
//error
}
}
我在 StackOverflow 上看到了这个问题:转换普通带有 Async 和 Await 的 Http Post Web 请求,但我无法正确理解答案.
I saw this question on StackOverflow: Converting ordinary Http Post web request with Async and Await, but I could not understand the answer properly.
请问有人可以帮忙吗?我真的很感激!
Please can anyone help? I would be really grateful!
推荐答案
您可以使用 TaskFactory.FromAsync
到 将APM转换为TAP,制作了很多这样的小扩展方法:
You can use TaskFactory.FromAsync
to convert APM to TAP, making a lot of tiny extension methods like this:
public static Task<Stream> GetRequestStreamAsync(this WebRequest request)
{
return TaskFactory.FromAsync(request.BeginGetRequestStream, request.EndGetRequestStream, null);
}
并对 WebRequest.GetResponse
和(如有必要)Stream.Write
、Stream.Flush
等执行相同的操作.
and do the same for WebRequest.GetResponse
and (if necessary) Stream.Write
, Stream.Flush
, etc.
然后您可以使用 async
和 await
编写您的实际逻辑,无需任何回调:
Then you can write your actual logic using async
and await
without any callbacks:
public async Task DefLoginAsync()
{
postData = "My Data To Post";
var url = new Uri("Url To Post to", UriKind.Absolute);
webRequest = WebRequest.Create(url);
webRequest.Method = "POST";
webRequest.ContentType = "text/xml";
using (Stream postStream = await webRequest.GetRequestStreamAsync())
{
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
await postStream.WriteAsync(byteArray, 0, byteArray.Length);
await postStream.FlushAsync();
}
try
{
string Response;
using (var response = (HttpWebResponse)await webRequest.GetResponseAsync());
using (Stream streamResponse = response.GetResponseStream())
using (StreamReader streamReader = new StreamReader(streamResponse))
{
Response = await streamReader.ReadToEndAsync();
}
if (Response == "")
{
//show some error msg to the user
Debug.WriteLine("ERROR");
}
else
{
//Your response will be available in "Response"
Debug.WriteLine(Response);
}
}
catch (WebException)
{
//error
}
}
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