❔ variable refusing to increment

Sander · 2023-10-07T10:50:27.275Z

ive got a variable inside my blazor component that refuses to increment itself inside a while loop of a PeriodicTimer. a copy of my code (the file) with the relevant methods and fields is below, inside the screenshot you can see the result when im running this. any answer to help me understand what is going on here would be greatly appriciated

C

canton7•10/7/23, 11:17 AM

Have you tried to figure out which bit is causing the problem?

If you replace the
```
await TriggerOnTimeSelect
```
await TriggerOnTimeSelect
```
await TriggerOnTimeSelect
```
await TriggerOnTimeSelect
with something else (e.g.
```
await Task.Delay(100)
```
await Task.Delay(100)
```
await Task.Delay(100)
```
await Task.Delay(100)
), does it still happen?
If you replace the
```
await OnTimeSelect(selectedTimeOfDay);
```
await OnTimeSelect(selectedTimeOfDay);
```
await OnTimeSelect(selectedTimeOfDay);
```
await OnTimeSelect(selectedTimeOfDay);
with something else, does it still happen?
If you don't bind
```
sliderValue
```
sliderValue
```
sliderValue
```
sliderValue
to the
```
input
```
input
```
input
```
input
, does it still happen?

T

TheRanger•10/7/23, 11:30 AM

try this

    async Task RunTimer()
    {
        while (await periodicTimer.WaitForNextTickAsync(updateTimerCancellationToken) && !updateTimerCancellationToken.IsCancellationRequested)
        {
            int localSliderValue = sliderValue;
            Console.WriteLine($"");
            Console.WriteLine($"before increment: {localSliderValue}");

            localSliderValue++;
            currentTimeInMinutes++;

            Console.WriteLine($"after increment: {localSliderValue}");

            await TriggerOnTimeSelect(DateTime.Now.Second);

            Console.WriteLine($"after function call: {localSliderValue}");

            sliderValue = localSliderValue;
        }
    }

    async Task RunTimer()
    {
        while (await periodicTimer.WaitForNextTickAsync(updateTimerCancellationToken) && !updateTimerCancellationToken.IsCancellationRequested)
        {
            int localSliderValue = sliderValue;
            Console.WriteLine($"");
            Console.WriteLine($"before increment: {localSliderValue}");

            localSliderValue++;
            currentTimeInMinutes++;

            Console.WriteLine($"after increment: {localSliderValue}");

            await TriggerOnTimeSelect(DateTime.Now.Second);

            Console.WriteLine($"after function call: {localSliderValue}");

            sliderValue = localSliderValue;
        }
    }

    async Task RunTimer()
    {
        while (await periodicTimer.WaitForNextTickAsync(updateTimerCancellationToken) && !updateTimerCancellationToken.IsCancellationRequested)
        {
            int localSliderValue = sliderValue;
            Console.WriteLine($"");
            Console.WriteLine($"before increment: {localSliderValue}");

            localSliderValue++;
            currentTimeInMinutes++;

            Console.WriteLine($"after increment: {localSliderValue}");

            await TriggerOnTimeSelect(DateTime.Now.Second);

            Console.WriteLine($"after function call: {localSliderValue}");

            sliderValue = localSliderValue;
        }
    }

    async Task RunTimer()
    {
        while (await periodicTimer.WaitForNextTickAsync(updateTimerCancellationToken) && !updateTimerCancellationToken.IsCancellationRequested)
        {
            int localSliderValue = sliderValue;
            Console.WriteLine($"");
            Console.WriteLine($"before increment: {localSliderValue}");

            localSliderValue++;
            currentTimeInMinutes++;

            Console.WriteLine($"after increment: {localSliderValue}");

            await TriggerOnTimeSelect(DateTime.Now.Second);

            Console.WriteLine($"after function call: {localSliderValue}");

            sliderValue = localSliderValue;
        }
    }

T

TheRanger•10/7/23, 11:31 AM

i stumbled through similiar issues before usually because of async and using local variables usually fixes it

D

DΣX•10/7/23, 11:32 AM

try using the volatile keyword for these variables that are incremented

T

TheRanger•10/7/23, 11:33 AM

never heard of that keyword before

D

DΣX•10/7/23, 11:33 AM

also these may help:
https://learn.microsoft.com/en-us/dotnet/api/system.threading.interlocked.increment?view=net-7.0

Interlocked.Increment Method (System.Threading)

Increments a specified variable and stores the result, as an atomic operation.

D

DΣX•10/7/23, 11:34 AM

its just based upon an assumption that you are updating them from different threads which for some orderly reasons writes back the old value after increment.
but its just a guess, and worth a try

C

canton7•10/7/23, 11:35 AM

Volatile shouldn't make any difference. It's not being updated from multiple threads at the same time, and awaits put in a memory barrier anyway

Ccanton7 Volatile shouldn't make any difference. It's not being updated from multiple thr...

D

DΣX•10/7/23, 11:36 AM

what is your idea on why its not incrementing?

C

canton7•10/7/23, 11:36 AM

(and volatile isn't the answer to threading issues anyway: what it does is very nuanced and depends on the memory model of the platform, and the advice is not to use it)

C

canton7•10/7/23, 11:37 AM

My guess is that it's something to do with the fact that it's bound to a control, and code is invoked when the control changes. Or maybe that OnTimeSelect which we can't see. Hence my suggestions

C

canton7•10/7/23, 11:38 AM

Easy to test: remove the binding / call to OnTimeSelect, see if the field starts behaving

T

TheRanger•10/7/23, 11:43 AM

i would also change it to a property, then set a breakpoint on the setter to see what sets it back

D

DΣX•10/7/23, 11:43 AM

i wouldnt suggest using volatile either. was just a way to figure out if it is maybe thread related. as soon as you have await in some code, threads may not be the same anymore after is. so in each loop he may be in a different thread.

D

DΣX•10/7/23, 11:44 AM

the binding is a good call as well

S

SanderOP•10/7/23, 12:14 PM

Thank you all for your replies, i'll test the things mentioned and come back with results

U

UltraWelfare•10/7/23, 5:02 PM

I think the problem relies on the fact that none of the rerender rules apply so blazor doesn't rerender

U

UltraWelfare•10/7/23, 5:05 PM

you can use statehaschanged

U

UltraWelfare•10/7/23, 5:05 PM

inside runtimer

U

UltraWelfare•10/7/23, 5:07 PM

or you can change your OnTimeSelect to be an EventCallback instead of a Func. However this will make the parent component rerender which might not be ideal for you... In the case where you only want to update this component use the statehaschanged as i've explained

A

Accord•10/8/23, 5:32 PM

Was this issue resolved? If so, run

/close

/close

otherwise I will mark this as stale and this post will be archived until there is new activity.

❔ variable refusing to increment

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