[英]IAsyncResult returned from Begin method is null?
如果我收到一些错误,我需要返回null。 但这引发了
IAsyncResult returned from Begin method is null.
这是我的代码?
try
{
var url = (string)state;
var request = (HttpWebRequest)WebRequest.Create(url);
return request.BeginGetResponse(cb, request);
}
catch (Exception ex)
{
}
return null;
如何返回空的IAsyncResult?
只需实现此界面即可。
public class NullAsyncResult : IAsyncResult
{
public object AsyncState
{
get { return null; }
}
public System.Threading.WaitHandle AsyncWaitHandle
{
get { return null; }
}
public bool CompletedSynchronously
{
get { return true; }
}
public bool IsCompleted
{
get { return true; }
}
}
然后在你的代码中:
try
{
var url = (string)state;
var request = (HttpWebRequest)WebRequest.Create(url);
return request.BeginGetResponse(cb, request);
}
catch (Exception ex)
{
}
return NullAsyncResult();
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