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[英]Can a WCF duplex service determine if the callback channel of a client has implemented a specific method before the service tries to call it?
[英]Call request/reply method of duplex service freeze client until timeout occur
我已经创建了一个双工WCF服务,可以将数据从外部设备返回到客户端,并且还允许请求/答复呼叫。
我的问题是请求/答复调用有时会冻结客户端,直到发生超时。
这些是接口:
[ServiceContract(CallbackContract = typeof(ITimerServiceCallback), SessionMode = SessionMode.Required)]
public interface ITimerService
{
[OperationContract]
void StartTimer();
[OperationContract]
void StopTimer();
[OperationContract]
void DoOp();
}
public interface ITimerServiceCallback
{
[OperationContract(IsOneWay = true)]
void ReportTick(string now);
}
这是实现:
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class TimerService : ITimerService
{
public TimerService()
{
_timer = new System.Timers.Timer() { Interval = 500 };
_timer.Elapsed += Timer_Elapsed;
}
private void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
_context.GetCallbackChannel<ITimerServiceCallback>().ReportTick(DateTime.Now.ToString());
}
private readonly System.Timers.Timer _timer;
private OperationContext _context;
public void StartTimer()
{
_context = OperationContext.Current;
_timer.Start();
}
public void StopTimer()
{
_timer.Stop();
}
public void DoOp()
{
System.Threading.Thread.Sleep(200);
}
}
重现此问题的步骤:*调用StartTimer *调用DoOp(一个或多个时间直到客户端冻结)
一分钟后,我有一个超时异常。
如果我从客户端使用异步/等待,一切正常。
例如:DoOp方法以这种方式调用:
private async void _btnDoOp_Click(object sender, EventArgs e)
{
_btnNoOp.Enabled = false;
try {
Task task = Task.Run(() => _client.DoOperation());
await task;
} catch (Exception ex) {
MessageBox.Show(ex.Message);
} finally {
_btnNoOp.Enabled = true;
}
}
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