1
我正在做一個簡單的應用程序來連接到web服務，並且我在管理異步請求時遇到問題。如何在不阻塞主線程的情況下返回異步HttpWebResponse？
問題在於函數ProcessRequest，它基本上使異步HttpWebRequest，並返回HttpWebResponse。由於請求是異步的，我在返回值方面遇到了問題，並且調用了ProcessRequest方法並等待HttpWebResponse對象。
順便說一下，請求本身工作完美，已經在功能內測試，所以我不需要返回HttpWebResponse。
我希望自己清楚，正如我所說，這是我第一次觸摸c＃，.NET和Windows Phone開發。 （和WebRequests爲此事）
的錯誤是Visual Studio是拋是：
1: Since 'System.AsyncCallback' returns void, a return keyword must not be followed by an object expression
2: Cannot convert lambda expression to delegate type 'System.AsyncCallback' because some of the return types in the block are not implicitly convertible to the delegate return type
這是代碼：
namespace SimpleNoteConcept
{
public sealed class SimpleNote
{
private static readonly SimpleNote _instance = new SimpleNote();
private static string _authToken = string.Empty;
private static string _email = string.Empty;
private static string _authQsParams
{
get
{
if (string.IsNullOrEmpty(_authToken)) throw new SimpleNoteConceptAuthorisationException();
return string.Format("auth={0}&email={1}", _authToken, _email);
}
}
private SimpleNote() { }
public static SimpleNote Instance
{
get { return _instance; }
}
public bool Connect(string email, string password)
{
try
{
StringParamCheck("email", email);
StringParamCheck("password", password);
var data = string.Format("email={0}&password={1}", email, password);
var bytes = Encoding.GetEncoding("utf-8").GetBytes(data);
data = Convert.ToBase64String(bytes);
using (var resp = ProcessRequest(loginPath, "POST", content: data))
{
if (resp != null)
{
_authToken = resp.Cookies["auth"].Value;
_email = email;
System.Diagnostics.Debug.WriteLine("Connection established! -> " + _authToken);
return true;
}
return false;
}
}
catch (Exception)
{
throw;
}
}
public void GetIndex(int length = 100, string mark = null, DateTimeOffset? since = null)
{
try
{
string sinceString = null;
if (since.HasValue)
sinceString = Json.DateTimeEpochConverter.DateToSeconds(since.Value);
var queryParams = string.Format("{0}&length={1}&mark={2}&since={3}", _authQsParams, length, mark, sinceString);
using (var resp = ProcessRequest(indexPath, "GET", queryParams))
{
var respContent = ReadResponseContent(resp);
System.Diagnostics.Debug.WriteLine("GetIndex: " + respContent.ToString());
//var notes = JsonConvert.DeserializeObject<Objects.NoteEnumerable<T>>(respContent);
//return notes;
}
}
catch (WebException ex)
{
var resp = (HttpWebResponse)ex.Response;
switch (resp.StatusCode)
{
//401
case HttpStatusCode.Unauthorized:
throw new SimpleNoteConceptAuthorisationException(ex);
default:
throw;
}
}
catch (Exception) { throw; }
}
/// <summary>
/// Generic method to process a request to Simplenote.
/// All publicly expose methods which interact with the store are processed though this.
/// </summary>
/// <param name="requestPath">The path to the request to be processed</param>
/// <param name="method">The HTTP method for the request</param>
/// <param name="content">The content to send in the request</param>
/// <param name="queryParams">Queryparameters for the request</param>
/// <returns>An HttpWebResponse continaing details returned from Simplenote</returns>
private static HttpWebResponse ProcessRequest(string requestPath, string method,
string queryParams = null, string content = null)
{
try
{
var url = string.Format("{0}{1}{2}", "https://", domainPath, requestPath);
if (!string.IsNullOrEmpty(queryParams)) url += "?" + queryParams;
var request = WebRequest.Create(url) as HttpWebRequest;
request.CookieContainer = new CookieContainer();
request.Method = method;
request.BeginGetRequestStream((e) =>
{
using (Stream stream = request.EndGetRequestStream(e))
{
// Write data to the request stream
var bytesBody = Encoding.GetEncoding("utf-8").GetBytes(content);
stream.Write(bytesBody, 0, bytesBody.Length);
stream.Close();
stream.Dispose();
}
request.BeginGetResponse((callback) =>
{
try
{
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(callback);
return response;
}
catch (WebException ex)
{
using (WebResponse Exresponse = ex.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)Exresponse;
System.Diagnostics.Debug.WriteLine("Error code: {0}", httpResponse.StatusCode);
using (Stream str = Exresponse.GetResponseStream())
{
string text = new StreamReader(str).ReadToEnd();
System.Diagnostics.Debug.WriteLine(text);
}
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("Message: " + ex.Message);
}
}, request);
}, request);
}
catch (Exception)
{
throw;
}
}
/// <summary>
/// Reads the content from the response object
/// </summary>
/// <param name="resp">The response to be processed</param>
/// <returns>A string of the response content</returns>
private static string ReadResponseContent(HttpWebResponse resp)
{
if (resp == null) throw new ArgumentNullException("resp");
using (var sr = new StreamReader(resp.GetResponseStream()))
{
return sr.ReadToEnd();
}
}
/// <summary>
/// String parameter helper method.
/// Checks for null or empty, throws ArgumentNullException if true
/// </summary>
/// <param name="paramName">The name of the paramter being checked</param>
/// <param name="value">The value to check</param>
private void StringParamCheck(string paramName, string value)
{
if (string.IsNullOrEmpty(value)) throw new ArgumentNullException(paramName, "Value must not be null or string.Empty");
}
} // Class End
} // Namespace End
提前感謝！
你的ProcessRequest方法會在你的委託甚至執行之前完成，對嗎？我認爲你需要在C＃5中使用新的異步/等待功能，但是我從來沒有親自使用過它們，也不確定它們是否可用於WP7 7.1 ... http://www.codeproject.com/Articles/127291/C-5-0-vNext-New-Asynchronous-Pattern –
這可能有助於簡化異步代碼，但由於它仍然是CTP，我不會實現它。不管怎麼說，還是要謝謝你。 是的，它可用於WP7平臺。 – asendra