c# - Observe for ItemChanged on two ReactiveLists -

i have viewmodel in listen changes items in 2 reactivelists, payments , accountpayments. lists instantiated , changetrackingenabled set true:

this.payments = new reactivelist<transaction.paymentviewmodel>(); this.payments.changetrackingenabled = true;` this.accountpayments = new reactivelist<accountpaymentviewmodel>(); this.accountpayments.changetrackingenabled = true;` 

then, defined in viewmodel, have observableaspropertyhelper readonly property:

readonly observableaspropertyhelper<decimal> _totalpayments; public decimal totalpayments { { return _totalpayments.value; } } 

my intent set totalpayments whenever of these items change in both lists. tried using whenany:

this.whenany(vm => vm.payments.itemchanged,             vm => vm.accountpayments.itemchanged,             (a, b) => a.sender.payments                 .where(x => x.amount.hasvalue).sum(x => x.amount.value)                 + b.sender.accountpayments                 .where(x => x.amount.hasvalue).sum(x => x.amount.value))             .toproperty(this, vm => vm.totalpayments, out _totalpayments); 

while compiles fine, doesn't seem catch changes. tried using whenanyobservable:

this.whenanyobservable(             vm => vm.payments.itemchanged,             vm => vm.accountpayments.itemchanged)             .select(_ =>                 this.payments.where(x => x.amount.hasvalue)                     .sum(x => x.amount.value)                 + this.accountpayments.where(x => x.amount.hasvalue)                     .sum(x => x.amount.value))             .toproperty(this, vm => vm.totalpayments, out _totalpayments); 

but won't compile. there way accomplish trying do? appreciated.

the first won't work it's observing property changes , itemchanged won't change, it's observable.

the second pretty correct, requires bit of modification. whenanyobservable requires observables same type. you're uninterested in actual result, can select unit , merge two:

this.whenanyobservable(a => a.payments.itemchanged).select(_ => unit.default)     .merge(this.whenanyobservable(a => a.accountpayments.itemchanged).select(_ => unit.default)); 

you can't select unit.default within whenanyobservable re-writes expression observe property changes make sure has latest observable. if neither payments nor accountpayments change (i.e. they're read only), can omit whenanyobservable altogether:

payments.itemchanged.select(_ => unit.default)     .merge(accountpayments.itemchanged.select(_ => unit.default));