我有点困惑。我正在尝试以异步方式发布到我的网络服务，理想情况下我想启动请求，在 UI 上显示加载微调器，然后当异步请求完成时处理响应，并且如果有错误则显示错误，或对结果进行其他操作。
这是我的代码，我在这里调用请求并传递一些数据。
private void SignInExecute()
{
if (Username == null || Password == null)
{
LoginOutput = "Please provide a username or password.";
}
else
{
this.webService.SendLoginRequest("http://localhost:3000/client_sessions", "username=" + Username + "&password=" + Password);
}
}
这是实际的网络请求代码：
public void SendLoginRequest(string url, string postdata)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.Accept = "application/json";
byte[] byteArray = Encoding.UTF8.GetBytes(postdata);
request.CookieContainer = new CookieContainer();
request.ContentLength = byteArray.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(byteArray, 0, byteArray.Length);
dataStream.Close();
((HttpWebRequest)request).KeepAlive = false;
request.BeginGetResponse(new AsyncCallback(GetLoginResponseCallback), request);
}
private static void GetLoginResponseCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
Stream streamResponse = response.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string responseString = streamRead.ReadToEnd();
Console.WriteLine(responseString);
// Close the stream object
streamResponse.Close();
streamRead.Close();
response.Close();
}
所以总结一下。我希望能够将响应返回到最初调用 Web 请求启动的对象。有什么帮助吗？
你需要告诉BeginGetResponse返回到通过以下方式调用它的相同上下文SynchronizationContext.Current。像这样的东西（代码没有适当的错误检查，所以你应该正确地考虑这一点）（此外，Platinum Azure 是正确的，你应该使用using让您的流正确关闭（并保证）：
在您的 SendLoginRequest 中：
//Box your object state with the current thread context
object[] boxedItems = new []{request, SynchronizationContext.Current};
request.BeginGetResponse(new AsyncCallback(GetLoginResponseCallback),
boxedItems);
获取响应代码：
private static void GetLoginResponseCallback(IAsyncResult asynchronousResult)
{
//MY UPDATE
//Unbox your object state with the current thread context
object[] boxedItems = asynchronousResult.AsyncState as object[];
HttpWebRequest request = boxedItems[0] as HttpWebRequest;
SynchronizationContext context = boxedItems[1] as SynchronizationContext;
// End the operation
using(HttpWebResponse response =
(HttpWebResponse)request.EndGetResponse(asynchronousResult))
{
using(Stream streamResponse = response.GetResponseStream())
{
using(StreamReader streamRead = new StreamReader(streamResponse))
{
string responseString = streamRead.ReadToEnd();
Console.WriteLine(responseString);
//MY UPDATE
//Make an asynchronous call back onto the main UI thread
//(context.Send for a synchronous call)
//Pass responseString as your method parameter
//If you have more than one object, you will have to box again
context.Post(UIMethodToCall, responseString);
}
}
}
}
实现您的 UI 处理
public static void UIMethodCall(object ObjectState)
{
String response = ObjectState as String;
label1.Text = String.Format("Output: {0}", response);
//Or whatever you need to do in the UI...
}
不过，现在我会先测试一下。我对 Microsoft 事件驱动异步实现的理解是，响应是上下文感知的，并且知道要返回哪个上下文。因此，在假设您不在同一上下文中之前，请尝试更新 UI 进行测试（如果您不在调用 (UI) 线程上，这将导致线程上下文异常）
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