Execption raises when asynchronous call to a dependent propertie about fsharp.viewmodule

[ReedCopsey]

WPF is very "fussy" about threading issues. Simple properties can be set from other threads, but anything that touches the UI in more convoluted ways (commands, collections, etc) must always be set, or at least notified, from the UI thread.

In this case, it's the Command's CanExecuteChanged event - that needs to happen on the UI thread.

We don't track the current context within every command - it adds quite a bit of overhead. However, the dependency notification system does provide a mechanism to allow this. Unfortunately, it got hidden in the major API update recently.

I've just pushed Version 1.0.6 to NuGet ( https://www.nuget.org/packages/FSharp.ViewModule.Core/1.0.6 ), which re-exposes this.

With this release, you can now make any ViewModel become "thread aware" on an opt-in basis by adding a single line of code. Just change your definition to:

type MyViewModel () as this =
    inherit ViewModelBase ()
    do
        this.DependencyTracker.SynchronizationContext <- System.Threading.SynchronizationContext.Current

    // ... rest of your code here

This causes all dependent property notifications to post to the UI thread, which should solve your issue.

[ReedCopsey]

Going to close this - feel free to reopen if you're still having issues, or ask if you need more clarification.

[Ummon]

Thanks for your answer. It solves my problem.