我使用DownloadStringAsync()
进行网络请求,但我只需在调用DownloadStringCompleted
事件时返回结果。在downloadasync-method之后,我需要等待结果,然后我可以在字符串属性中返回它。所以我实现了while(Result == "")
,但我不知道该怎么做。我已经尝试了Thread.sleep(500)
,但似乎下载永远不会完成。而且代码永远存在。
string Result = "";
public String Query(DataRequestParam dataRequestParam)
{
try
{
WebClient web = new WebClient();
if (!string.IsNullOrEmpty(dataRequestParam.AuthentificationLogin))
{
System.Net.NetworkCredential account = new NetworkCredential(dataRequestParam.AuthentificationLogin, dataRequestParam.AuthentificationPassword);
web.Credentials = account;
}
web.DownloadStringCompleted += OnDownloadStringCompleted;
web.DownloadStringAsync(dataRequestParam.TargetUri);
while (Result == "")
{
//What am i supposed to do here ?
}
return Result;
}
catch(WebException we)
{
MessageBox.Show(we.Message);
return null;
}
}
private void OnDownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Error != null)
{
//Error treating
}
else
{
Result = e.Result;
}
}
UI代码
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
if (e.NavigationMode != NavigationMode.Back)
{
ServerFunctions.SetUserProfil(User.UserLogin,User.UserPassword);
this.listBoxGetDocsLibs.Clear();
List<BdeskDocLib> list = new List<BdeskDocLib>();
try
{
//HERE THE START OF THE DOWNLOAD
ServerFunctions.GetDocLibs(true);
}
catch (Exception ex)
{
//error
}
foreach (BdeskDocLib docLib in list)
{
this.listBoxGetDocsLibs.Add(docLib);
}
}
}
ServerFunction静态类
public static List<BdeskDocLib> GetDocLibs(bool onlyDocLibPerso)
{
string xmlContent = GetXml(URL_GETDOCLIBS);
List<BdeskDocLib> result = BdeskDocLib.GetListFromXml(xmlContent, onlyDocLibPerso);
return result;
}
private static String GetXml(string partialUrl)
{
string url = GenerateUrl(partialUrl);
DataRequestParam dataRequestParam = new DataRequestParam();
dataRequestParam.TargetUri = new Uri(url);
dataRequestParam.UserAgent = "BSynchro";
dataRequestParam.AuthentificationLogin = userLogin;
dataRequestParam.AuthentificationPassword = userPwd;
//HERE I START THE QUERY method
// NEED QUERY RETURNS A STRING or Task<String>
DataRequest requesteur = new DataRequest();
xmlResult=requesteur.Query(dataRequestParam);
if (CheckErrorConnexion(xmlResult) == false)
{
throw new Exception("Erreur du login ou mot de passe");
}
return xmlResult;
}
答案 0 :(得分:0)
阻止主UI没有什么好处(除非你真的需要)。但是如果你想等待你的结果你可以使用async-await和TaskCompletitionSource - 你可以找到more about on this blog和how to use TCS in this answer:
public static Task<string> myDownloadString(DataRequestParam dataRequestParam)
{
var tcs = new TaskCompletionSource<string>();
var web = new WebClient();
if (!string.IsNullOrEmpty(dataRequestParam.AuthentificationLogin))
{
System.Net.NetworkCredential account = new NetworkCredential(dataRequestParam.AuthentificationLogin, dataRequestParam.AuthentificationPassword);
web.Credentials = account;
}
web.DownloadStringCompleted += (s, e) =>
{
if (e.Error != null) tcs.TrySetException(e.Error);
else if (e.Cancelled) tcs.TrySetCanceled();
else tcs.TrySetResult(e.Result);
};
web.DownloadStringAsync(dataRequestParam.TargetUri);
return tcs.Task;
}
public async Task<string> Query(DataRequestParam dataRequestParam)
{
string Result = "";
try
{
Result = await myDownloadString(dataRequestParam);
}
catch (WebException we)
{
MessageBox.Show(we.Message);
return null;
}
return Result;
}
(我没试过这个代码,可能会有一些错误,但它应该有效)
基于此代码,您还可以使用等待版本的下载字符串扩展WebClient。