我有从服务器下载的文件时,它保存到独立存储异步并提供GetData方法来检索数据的对象。我会用一个异步HttpWebRequest的锁定
IsolatedStorageFile storageObj; //initialized in the constructor
lock(storageObj)
{
//save code
}
在响应和
lock(storageObj)
{
//load code
}
在GetData方法?
编辑:我会在这里提供一些背景。 应用程序(用于Windows Phone)需要从服务器下载并缓存多个文件,因此我创建了一个需要2个字符串(一个uri和一个文件名)的类型,从给定的uri发送数据并保存它。同一个对象也有get数据方法。下面的代码(简化一点)
public class ServerData: INotifyPropertyChanged
{
public readonly string ServerUri;
public readonly string Filename;
IsolatedStorageFile appStorage;
DownloadState _downloadStatus = DownloadState.NotStarted;
public DownloadState DownloadStatus
{
protected set
{
if (_downloadStatus == value) return;
_downloadStatus = value;
OnPropertyChanged(new PropertyChangedEventArgs("DownloadStatus"));
}
get { return _downloadStatus; }
}
public ServerData(string serverUri, string filename)
{
ServerUri = serverUri;
Filename = filename;
appStorage = IsolatedStorageFile.GetUserStoreForApplication();
}
protected virtual void OnPropertyChanged(PropertyChangedEventArgs args)
{
if (PropertyChanged != null)
PropertyChanged(this, args);
}
public void RequestDataFromServer()
{
DownloadStatus = DownloadState.Downloading;
//this first bit adds a random unused query to the Uri,
//so Silverlight won't cache the request
Random rand = new Random();
StringBuilder uriText = new StringBuilder(ServerUri);
uriText.AppendFormat("?YouHaveGotToBeKiddingMeHack={0}",
rand.Next().ToString());
Uri uri = new Uri(uriText.ToString(), UriKind.Absolute);
HttpWebRequest serverRequest = (HttpWebRequest)WebRequest.Create(uri);
ServerRequestUpdateState serverState = new ServerRequestUpdateState();
serverState.AsyncRequest = serverRequest;
serverRequest.BeginGetResponse(new AsyncCallback(RequestResponse),
serverState);
}
void RequestResponse(IAsyncResult asyncResult)
{
var serverState = (ServerRequestUpdateState)asyncResult.AsyncState;
var serverRequest = (HttpWebRequest)serverState.AsyncRequest;
Stream serverStream;
try
{
// end the async request
serverState.AsyncResponse =
(HttpWebResponse)serverRequest.EndGetResponse(asyncResult);
serverStream = serverState.AsyncResponse.GetResponseStream();
Save(serverStream);
serverStream.Dispose();
}
catch (WebException)
{
DownloadStatus = DownloadState.Error;
}
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
DownloadStatus = DownloadState.FileReady;
});
}
void Save(Stream streamToSave)
{
StreamReader reader = null;
IsolatedStorageFileStream file;
StreamWriter writer = null;
reader = new StreamReader(streamToSave);
lock (appStorage)
{
file = appStorage.OpenFile(Filename, FileMode.Create);
writer = new StreamWriter(file);
writer.Write(reader.ReadToEnd());
reader.Dispose();
writer.Dispose();
}
}
public XDocument GetData()
{
XDocument xml = null;
lock(appStorage)
{
if (appStorage.FileExists(Filename))
{
var file = appStorage.OpenFile(Filename, FileMode.Open);
xml = XDocument.Load(file);
file.Dispose();
}
}
if (xml != null)
return xml;
else return new XDocument();
}
}
如果是这种情况,为什么不同步做? – 2011-03-14 23:54:50
这将阻止用户界面线程 – 2011-03-16 18:39:51