Reloading Viewmodel from Another ViewModel for Tab Control

Question

I have created a TAB control as mentioned in MVVMCROSS Tab link.

For Ex: I have two tab ViewModels 'Search and Filter'.
FilterViewModel: Country and State results properties to bind in View.
SearchViewModel: Listing the available results to View by selected filters from FilterViewModel.

How to update Searchviewmodel SearchListing function from Filterviewmodel property changed ?

Edit : My sample Core function with Messenger code. But missing some work around! Please suggest

public class SearchWOViewModel  : MvxViewModel
{
    private readonly ISearchService _serachwo;
    private readonly IMvxMessenger _messenger;

    public SearchWOViewModel(ISearchService search, IMvxMessenger Messanger)
    {
        _serachwo = search;           
        Search = new SearchViewModel(_serachwo);
        Filter = new FilterViewModel(_serachwo, Search, Messanger);
    }
    private FilterViewModel _Filter;
    public FilterViewModel Filter { get { return _Filter; } set { _Filter = value; RaisePropertyChanged(() => Filter); } }

    private SearchViewModel _Search;
    public SearchViewModel Search { get { return _Search; } set { _Search = value; RaisePropertyChanged(() => Search); } }

}

public class FilterViewModel : MvxViewModel
{
    private readonly ISearchService _filterwo;
    private readonly IMvxMessenger messenger;
    private readonly MvxSubscriptionToken _token;

    public FilterViewModel(ISearchService search, SearchViewModel searchViewModel,IMvxMessenger _messenger)
    {
        _filterwo = search; messenger = _messenger;
        searchViewModel = SearchViewModel;
        SiteDropDown();         
        EquipmentDropDown();
    }

    public void SiteDropDown() { String query = "UserSite"; _filterwo.UserSite(query, result => { SiteResult = result; messenger.Publish(new UpdateSearchResultsMessage(this)); searchViewModel.SearchListingWO(); }, error => { }); }
    private List<DropDownEquipment> _siteresult;
    public List<DropDownEquipment> SiteResult { get { return _siteresult; } set { _siteresult = value; RaisePropertyChanged(() => SiteResult); } }

    public void EquipmentDropDown() { String query = "FillEquipment"; _filterwo.FillEquipment(query, result => { EquipmentResult = result; }, error => { }); }
    private List<DropDownEquipment> _EquipmentResults;
    public List<DropDownEquipment> EquipmentResult { get { return _EquipmentResults; } set { _EquipmentResults = value; RaisePropertyChanged(() => EquipmentResult); } }

    private DropDownEquipment _SelectedSite;
    public DropDownEquipment SelectedSite { get { return _SelectedSite; } set { _SelectedSite = value; RaisePropertyChanged(() => SelectedSite); } }
    private DropDownEquipment _SelectedEquipment;
    public DropDownEquipment SelectedEquipment { get { return _SelectedEquipment; } set { _SelectedEquipment = value; RaisePropertyChanged(() => SelectedEquipment); } }
}

public class SearchViewModel : MvxViewModel
{
    private readonly ISearchService _WorkOrder;
    public SearchViewModel(ISearchService search)
    {
        _WorkOrder = search;            
        SearchListingWO();
    }

    public void SearchListingWO() { String query = "WORKORDER"; _WorkOrder.Listingwo(query, result => Results = result, error => { }); }
    private List<ListingWo> _results;
    public List<ListingWo> Results { get { return _results; } set { _results = value; RaisePropertyChanged(() => Results); } }

    private ListingWo _SelectedWO;
    public ListingWo SelectedWO { get { return _SelectedWO; } set { _SelectedWO = value; RaisePropertyChanged(() => SelectedWO); } }
}

public class UpdateSearchResultsMessage : MvxMessage
{
    public UpdateSearchResultsMessage(object sender) : base(sender) { }
}

Please refer the sample code in MySampleTabCode. Kindly suggest/guide how to pass data.

Answer 1

What you are asking I think is basically how do you communicate between view models. There are few ways to do that:

1.You can have a custom message and send it from FilterViewModel to notify SearchViewModel. Look here for examples:

Executing UI Code from ViewModel on MVVMCross

http://slodge.blogspot.co.uk/2013/05/n9-getting-message-n1-days-of-mvvmcross.html

In your case you would have an UpdateSearchResultsMessage like

public class UpdateSearchResultsMessage : MvxMessage
{
     public UpdateSearchResultsMessage(object sender) : base(sender) {}
}

You will send this message from the SiteDropDown() method:

public void SiteDropDown()
{
      var messenger = Mvx.Resolve<IMvxMessenger>();
      String query = "UserSite";
     _filterwo.FillUserSite(query, result => { SiteResult = result; messenger.Publish(new UpdateSearchResultsMessage(this)); }, error => { });
}

Follow the instructions from the two links on how to register the message and how the SearchViewModel handles the message.

2.Much easier: Pass the SearchViewModel reference to the FilterViewModel in constructor:

  public SearchWOViewModel()
    {
        Search = new SearchViewModel(_serachwo);
        Filter = new FilterViewModel(_serachwo, Search);
    }

public class FilterViewModel : MvxViewModel
{
   public FilterViewModel(ISearchWOService search, SearchViewModel searchViewModel)
   {
      _filterwo = search;
      searchViewModel = SearchViewModel;
      SiteDropDown();
   }

    public void SiteDropDown()
    {
       String query = "UserSite";
      _filterwo.FillUserSite(query, result => { SiteResult = result; searchViewModel.SearchListingWO(); }, error => { });
    }
}

A general observation: I don't know how your application works, but maybe consider instead of having two view models just one view model, SearchViewModel, which does both search and filtering the user site.

But maybe you have much more functionality in the two view models than you showed, and in this case it might justify separation.