QueryCancelToken from F# Program
How to get a reference ?
Comments
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This feature isn't supported from F#. QueryCancelToken in C# is implemented as an instance member, and in F# the query ends up in a static method.
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Got a workaround here then ?
The below is a bit of test code to show what I'm trying to achieve. Copy-Paste straight into LP to run.
I want to be able to soft stop the query or if an error happens on a background thread also stop the query, and show the exception.
If a background thread throws (after 5sec in the example) then all is ok.
If I soft stop before 5 seconds. The awaiter remains and I get weird behaviour on next run.
I did think that if I could incorporate the QueryCancelToken that would help kill the awaiter on a soft close. But if that is a non option in F# Program then can you see another way ?open System.Threading.Tasks
let tcs = TaskCompletionSource()
Task.Run(fun () -> //mimicking some background work on a thread I dont control
Thread.Sleep(5000) //arbitary delay for the purposes of this excersise
tcs.SetException(InvalidCastException()) //an exception has been caught so lets give it to the tcs
)
task {
let d = Util.KeepRunning(true) //keep the query running to make the soft stop available
try
do! tcs.Task //wait for any background thread to throw (or complete normally)
with e ->
d.Dispose() //background thread threw, so dispose of soft close and end the query
raise e //re throw the error so LP shows it in the Results
} -
If you set Util.NewProcess to true, it should prevent any residue from effecting subsequent runs.
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Did think about that, but that also kills all state between executions. Will have to work with that for now.
