RaiseCanExecuteChanged does not fire? about fsharp.viewmodule

[isaacabraham]

My bad. I have a bit of time tomorrow and I'll try to repro it, or close if I can't.

[FoggyFinder]

@isaacabraham Can you provide MCVE?

[isaacabraham]

At the moment, no - at this point, before I do that, I'm just trying to understand if what I'm doing is correct i.e. should calling RaiseCanExecuteChange() on a command force WPF to call CanExecuteChanged on the command?

[giuliohome]

Maybe it's just a typo, but in the first command (the one that executes) you raise the Changed of the second (the one that you want to force recheck). It looks like you wrote the opposite : -)

[isaacabraham]

@giuliohome good spot - fixed :-)

[FoggyFinder]

I just can't understand the problem, maybe you want to use dependencies?

[isaacabraham]

@FoggyFinder that's what I was using originally but due to the way that the view model is now working, it's not possible any more - hence why I'm now explicitly trying to force the second command to refresh it's can execute state.

[ReedCopsey]

Does the command have a parameter? You'll get a silent fail if the parameter can't be coerced to the right type. That being said, I'd highly recommend using a dependency. The method you're calling can always set a dependency to the right value, which in turn will handle the command...

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On Mon, Jan 2, 2017 at 6:06 AM, Isaac Abraham ***@***.***> wrote: @FoggyFinder <https://github.com/FoggyFinder> that's what I was using originally but due to the way that the view model is now working, it's not possible any more - hence why I'm now explicitly trying to force the second command to refresh it's can execute state. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#26 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFCUmkoSrn022lydu1VjFp86Ek2Ogq8lks5rOQR5gaJpZM4LZArq> .

[ReedCopsey]

@isaacabraham Any update on this? Want to figure out whether it's a problem in the library, or something else...

[ReedCopsey]

@isaacabraham Thanks - Just don't want to leave you in the dark if it's something I can fix

[isaacabraham]

Here's a simple repro: -

https://github.com/isaacabraham/viewmodel-command

[ReedCopsey]

@isaacabraham The problem is that you weren't actually ever calling RaiseCanExecuteChanged on the instance bound in the view. Since you were creating the command directly in the property get code, a new instance is constructed each time you call vm.DependentCommand - that new instance becomes enabled, but the view still was holding onto the original instance.

I've put in a PR against your repo to illustrate how to fix, with comments.

[isaacabraham]

Thanks for this @ReedCopsey - much appreciated!