Wpf & PropertyInfo - CanWrite has changed

[ajohnstone-ks]

We have a BO, and there are actions users can do that take time, so we have pushed those to an eventual consistency model. The BO when loading will check if there are any unprocessed actions and record that into the BO into a field Locked. The BO also has a method that the UI can call RefreshLocked which will do a data portal call to see if the background work has finished or not. The Locked property has an Async property rule which when then manually trigger when the RefreshLocked is called.

We also have authorization rules on all writable properties, which at the very least check the Locked property, and deny permission for WriteProperty if Locked is true.

Now for WinForms we use the Csla ReadWriteAuthorization component and have the form listen to the BOs PropertyChanged, and if Lockedhas changed, callResetControlAuthorization` which then enables the previously disabled controls.

We're now trying to do something similar in Wpf; for each control we have a Csla Wpf PropertyInfo control, and the editor control binds its IsEnabled or IsReadOnly to the CanWrite of the PropertyInfo control. This works when intially loading the page, but its not quite clear to me how to let the PropertyInfos know that the CanWrite has changed. Do we just need to raise a PropertyChanged from the BO? Have the xaml page listen for the models propertychanged of Locked and find all the property infos?

[rockfordlhotka]

My recollection is that PropertyInfo handles the PropertyChanged event so it knows when to update its own values - and then it raises appropriate events to get the UI data binding to update.

[ajohnstone-ks]

I thought I saw code that it would also react to the BO's IsBusy changing and would update all of its properites, but that doesn't seem to be the case.

To fix our issue, I do await BusinessRules.CheckRulesAsync(LockedProperty) and then follow up with a OnPropertyChanged(string.Empty), that seems to cause all the csla:PropertyInfo on the page to re-examine the CanWrite. Does that seem like the correct approach, if there's nothing similar in Xaml to the WinForms ReadWriteAuthorization.ResetControlAuthorization ?

[rockfordlhotka]

CSLA has two modes for raising PropertyChanged - the WinForms way, which minimizes raising the event and often uses OnPropertyChanged(""). And the Xaml way, which raises the event on a per-property basis as much as possible.

This is because WPF (and other Xaml runtimes) actually used PropertyChanged "the right way" by looking at the name of the changed property, while WinForms always just refreshed all bindings regardless of what changed.

I'm pretty sure in CSLA 10 (and maybe 9) the property changed mode is set automatically based on the DI configuration in Program.cs. iirc, it used to be necessary to set the property changed mode yourself during app startup to get the correct behavior.

I don't know if this impacts what you are seeing, but it might.