C#•7mo ago

C# noob, trying to do a GUI app with a background service

Hello, what I am trying to do is: - Have a background connection to KSP (game) through a RPC library. - Plot live data coming from the connection I've used the WPF template from Rider, as it is the first one to choose from. At the moment I am trying to figure out how to have this background thread that updates the graph (using ScottPlot) This main loop is here: https://github.com/viperML/KspAutopilot/blob/2ad64786e8dd1bdb6457bf0b4e278b40b76b191e/MainWindow.xaml.cs Right now it "works", but closing window crashes with:

Unhandled exception. System.Threading.Tasks.TaskCanceledException: A task was canceled.
   at System.Windows.Threading.DispatcherOperation.Wait(TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherOperation operation, CancellationToken cancellationToken, TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.Invoke(Action callback, DispatcherPriority priority, CancellationToken cancellationToken, TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.Invoke(Action callback)
   at KspAutopilot.MainWindow.Work(Object sender, EventArgs e) in C:\Users\ayats\Documents\KspAutopilot\MainWindow.xaml.cs:line 45
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__128_1(Object state)
   at System.Threading.QueueUserWorkItemCallback.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()

Unhandled exception. System.Threading.Tasks.TaskCanceledException: A task was canceled.
   at System.Windows.Threading.DispatcherOperation.Wait(TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherOperation operation, CancellationToken cancellationToken, TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.Invoke(Action callback, DispatcherPriority priority, CancellationToken cancellationToken, TimeSpan timeout)
   at System.Windows.Threading.Dispatcher.Invoke(Action callback)
   at KspAutopilot.MainWindow.Work(Object sender, EventArgs e) in C:\Users\ayats\Documents\KspAutopilot\MainWindow.xaml.cs:line 45
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__128_1(Object state)
   at System.Threading.QueueUserWorkItemCallback.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()

Feel free to recommend any alternative to WPF or ScottPlot, as I just wanted to try the language as an alternative to python/matplotlib

33 Replies

WEIRD FLEX•7mo ago

first, you don't need Task.Run or better, you don't have any await in your code so i guess you do it because you want a thread...? also if you're using xaml you don't need to have async void your method can be async Task

Unknown User•7mo ago

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viper•7mo ago

catch what? ok, so I have moved the project WPF -> Avalonia, and changed to async Task: https://github.com/viperML/KspAutopilot/blob/d1e667c86cfdc43c77d40e49b0663f173018354a/MainWindow.axaml.cs also, connection was IDisposable and rider didn't tell me about it, so I didn't have using (I believe it was causing the connection to linger and not exiting the app) this thing seems to work (?), and when I close the window it terminates though I don't know if I am doing something wrong still

Unknown User•7mo ago

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viper•7mo ago

I don't know what you are saying about connection cut, I don't care about it I just wanted that closing the window would terminate the task and cleanup any resources cleanly

WEIRD FLEX•7mo ago

i'm not entirely sure but i think in this situation _ = Work() should do it still worth a try or even better, pass a cancellationToken to it

Unknown User•7mo ago

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WEIRD FLEX•7mo ago

exactly, that's why i pointed out that there is really no async code in there

Unknown User•7mo ago

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WEIRD FLEX•7mo ago

yeah, but at that point i would remove task.delay and make everything sync

Unknown User•7mo ago

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WEIRD FLEX•7mo ago

it changes that at least you know it's not really an async method

Unknown User•7mo ago

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WEIRD FLEX•7mo ago

you can do all that in a sync method except for task.delay which would be the usual thread.sleep

Unknown User•7mo ago

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MODiX•7mo ago

TeBeCo

I would still use await Task.Delay i would add a CTS and properly try/catch + call cancel and properly disconnect

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<@689473681302224947> from #C# noob, trying to do a GUI app with a background service (click here)

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WEIRD FLEX•7mo ago

ah wait that's true (although wouldn't a 100 msec sleep be a tragedy)

Unknown User•7mo ago

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WEIRD FLEX•7mo ago

i don't agree entirely, the matter to me is explicitness if you hide that this is not really an async method and you don't tell that this would have that kind of consequences (sync i/o), then make it sync and make a thread if for example the call connection.SpaceCenter(); had been async (and no i/o stuff in the ctor), then this _ = WorkAsync() would have been good OR name the method in a way that everyone understands this has to be started in a background thread

Unknown User•7mo ago

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viper•7mo ago

the C# is the reference implementation of KRPC, so I thought about using C# instead of going with the third-party ones

Unknown User•7mo ago

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viper•7mo ago

though I agree it's weird, and I have other problems with it

Unknown User•7mo ago

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viper•7mo ago

it's old as fuck though yeah

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viper•7mo ago

the 3rd-party rust libs also use a sync RPC connection, and not Futures so yeah

WEIRD FLEX•7mo ago

that's why i said "if the first line was an async call..."

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viper•7mo ago

I don't know how to do any of that, so I would be grateful if you point out some documentation about those I'll look for the documentation myself meanwhile

MODiX•7mo ago

TeBeCo

var cts = new CancellationTokenSource();
_ = Task.Run(async () => await WorkAsync(cts.Token))


/********************************************************/
// if you want to stop the taks:
cts.Cancel(); //will throw a TaskCancelledException, which is also an OperationCanceledException where it's using inside an await call, like the await Task.Delay(...., ct)
/********************************************************/

private async Task WorkAsync(CancellationToken ct)
{
  try
  {
    //the loop:
    while(!ct.IsCancellationRequested)
    {
      //the delay:
      await Task.Delay(duration, ct);
    }
  }
  catch(OperationCancelledException){} //  for the cts.Cancel()
  catch(Exception){} // for other exception
}

var cts = new CancellationTokenSource();
_ = Task.Run(async () => await WorkAsync(cts.Token))


/********************************************************/
// if you want to stop the taks:
cts.Cancel(); //will throw a TaskCancelledException, which is also an OperationCanceledException where it's using inside an await call, like the await Task.Delay(...., ct)
/********************************************************/

private async Task WorkAsync(CancellationToken ct)
{
  try
  {
    //the loop:
    while(!ct.IsCancellationRequested)
    {
      //the delay:
      await Task.Delay(duration, ct);
    }
  }
  catch(OperationCancelledException){} //  for the cts.Cancel()
  catch(Exception){} // for other exception
}

you could put a specific try/cach inside the loop itself if you want to handle re-connect

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viper•7mo ago

plot twist: this could even be done un App.cs or turned into a Host builder and use an IHostedService

the mention doesn't reference any of that

Unknown User•7mo ago

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C# noob, trying to do a GUI app with a background service