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我正在使用WebRequest.BeginGetResponse來從服務器下載文件的異步請求。所有作品都很好,但我不想同時下載5個文件。在Java中,我會使用固定的線程池,但我不知道如何在C#中執行相同的操作。有任何想法嗎?同時下載限制
class HttpFetcher
{
public void MakeRequest(Uri uri)
{
WebRequest request = WebRequest.Create(uri);
request.Proxy = null;
RequestState requestState = new RequestState();
requestState.Request = request;
IAsyncResult result = (IAsyncResult) request.BeginGetResponse(new AsyncCallback(ResponseCallback), requestState);
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, new WaitOrTimerCallback(TimeOutCallback), request, 1000, true);
}
private void ResponseCallback(IAsyncResult result)
{
try
{
RequestState requestState = (RequestState)result.AsyncState;
WebRequest request = requestState.Request;
requestState.Response = request.EndGetResponse(result);
Stream responseStream = requestState.Response.GetResponseStream();
requestState.ResponseStream = responseStream;
IAsyncResult asynchronousResultRead = responseStream.BeginRead(requestState.BufferRead, 0, 1024, new AsyncCallback(ReadCallback), requestState);
}
catch (Exception ex)
{
Console.WriteLine("Exception raised!");
Console.WriteLine("Message : {0}", ex.Message);
RequestState state = (RequestState)result.AsyncState;
if (state.Response != null)
state.Response.Close();
}
}
private void ReadCallback(IAsyncResult result)
{
try
{
RequestState requestState = (RequestState)result.AsyncState;
Stream responseStream = requestState.ResponseStream;
int bytesRead = responseStream.EndRead(result);
if (bytesRead > 0)
{
requestState.RequestData.Append(Encoding.ASCII.GetString(requestState.BufferRead, 0, bytesRead));
IAsyncResult asynchronousResult = responseStream.BeginRead(requestState.BufferRead, 0, 1024, new AsyncCallback(ReadCallback), requestState);
}
else
{
Console.WriteLine("\nThe HTML page Contents are: ");
if (requestState.RequestData.Length > 1)
{
string sringContent;
sringContent = requestState.RequestData.ToString();
//Console.WriteLine(sringContent);
}
Console.WriteLine("\nPress 'Enter' key to continue........");
responseStream.Close();
}
}
catch (WebException e)
{
Console.WriteLine("WebException raised!");
Console.WriteLine("\n{0}", e.Message);
Console.WriteLine("\n{0}", e.Status);
}
catch (Exception e)
{
Console.WriteLine("Exception raised!");
Console.WriteLine("Source : {0}", e.Source);
Console.WriteLine("Message : {0}", e.Message);
}
}
private void TimeOutCallback(object state, bool timedOut)
{
if (timedOut)
{
WebRequest request = (WebRequest)state;
if (state != null)
{
request.Abort();
}
}
}
}
這隻需要一個信號量,初始化爲5. WaitOne()在BeginGetResponse()調用之前,在完成回調中釋放()。 –
我用一些代碼更新了這個問題。我不知道在這個例子中是否可以使用你的解決方案@HansPassant –