c# - MvvmCross Xamarin-Forms Viewmodel return values and back navigation -

it's standard mvvm problem of getting results view-model.

mvvmcross v5's navigation service has brought in nice looking solutions this, i'm having trouble in practice. using xamarin-forms , testing android.

the setup main view button command bound calls second view gets value list.

https://www.mvvmcross.com/documentation/fundamentals/navigation

this page suggests new system using call new view , specify return type/value:

var result = await _navigationservice.navigate<newviewmodeltype, paramtype, resulttype>(param); 

which works nicely, in newviewmodeltype return (currently) says:

await _navigationservice.close(this, new resulttype()); // overload isn't there in 5.1 

that overload doesn't exist, can use close method of mvxviewmodel base (if anyone's hit issue):

 await close(new resulttype()); 

testing in android emulator works nicely when close using command.
if navigate away new view model button original button greyed out , never receive return value in main view.
i'd able press cancel out, button being disabled / await left hanging problem.

so how should handle this. there nice way return default on navigation? or there clean way intercept command , return default/null?

--

here actual bindings , relevant functions in case i've done dumb. operator here individual, not programming operator. view binding

<button text="{res:translate operator}" command="{binding selectoperatorcommand}" /> 

view model button command

public imvxcommand selectoperatorcommand =>     new mvxasynccommand(async () =>     {         var result = await _navigationservice.navigate<operatorselectviewmodel, operator, operator>(_operator);         operator = result; // never here if press in next view     }); 

the second view model (select list) init , close command

    public override task initialize(operator parameter)     {         _selectedoperator = parameter;         return base.initialize();     }      public imvxasynccommand closecommand =>         new mvxasynccommand(async () =>         {             await close(_selectedoperator);              // happy exit way.         });