mvvm - ReactiveCommand CanExecute reacting to changes in a collection -

mvvm - ReactiveCommand CanExecute reacting to changes in a collection -

i have reactivecollection filled items (that reactiveobjects well).

i want create reactivecommand should enabled when any of items in collection has property set true, like:

mycommand = reactivecommand.create( watch items in collection see if item.myprop == true )

so anytime there 1 of items property set true, command should enabled.

edit: thanks, paul. resulting code this:

public mainviewmodel() { items = new reactivelist<itemviewmodel> { new itemviewmodel("engine"), new itemviewmodel("turbine"), new itemviewmodel("landing gear"), new itemviewmodel("wings"), }; items.changetrackingenabled = true; var shouldbeenabled = items.createderivedcollection(x => x.isadded); var shouldrecheck = observable.merge( // when items added / removed / whatever shouldbeenabled.changed.select(_ => unit.default), // when of bools in coll alter shouldbeenabled.itemchanged.select(_ => unit.default)); // kick off check on startup shouldrecheck = shouldrecheck.startwith(unit.default); clearcommand = reactivecommand.create(shouldrecheck.select(_ => shouldbeenabled.any(x => x))); }

edit 2: i've discovered trap! if modify line:

new itemviewmodel("engine");

and set isadded = true this

new itemviewmodel("engine") { isadded = true };

… when run button disabled when application starts , it should enabled. seems look doesn't evaluate after alter occurs. how can solve it?

edit 3: solved! @paul-betts says, can solved adding line:

// kick off check on startup shouldrecheck = shouldrecheck.startwith(unit.default);

the code sample update above (and in answer, too).

how this

mysourcecollection.changetrackingenabled = true; shouldbeenabled = mysourcecollection.createderivedcollection(x => x.myprop); var shouldrecheck = observable.merge( // when items added / removed / whatever shouldbeenabled.changed.select(_ => unit.default), // when of bools in coll alter shouldbeenabled.itemchanged.select(_ => unit.default)); // kick off check on startup shouldrecheck = shouldrecheck.startwith(unit.default); mycmd = reactivecommand.create(shouldrecheck.select(_ => shouldbeenabled.all(x => x));

mvvm reactive-programming reactiveui