How can I switch views between viewmodels?

Question

My Main window defines the markup for the application, for this specific scenario lets say I have a grid with 2 columns.
First column will have navigation links, and second column will display the different views.
There are 2 views (and 2 viewmodels) defined in mainwindow xaml:

<Window.Resources>       
   <DataTemplate DataType="{x:Type vm:Window1ViewModel}">
       <vw:Window1View/>
   </DataTemplate>
   <DataTemplate DataType="{x:Type vm:Window2ViewModel}">
       <vw:Window2View/>
   </DataTemplate>      
</Window.Resources>

And in second grid column that displays the views i got :

<ContentControl  Content="{Binding Path=ViewModel}" HorizontalAlignment="Left">                    
</ContentControl>

Where ViewModel is a property that I set accordingly to a view(viewmodel) that i want to display.

Like :

ViewModel = new Window1ViewModel();
(datacontext of the mainwindowview is set to MainWindowViewModel)

So there is no problem to switch between views from the MainWindowViewModel.

My problem is how to switch within Window1ViewModel into Window1ViewMode2?

The various ViewModels don't "know" about other ViewModels.
Only MainWindowViewModel knos about others...

How can I solve this? Maybe I should define a custom Event (with parameter), MainWindowViewModel will subscribe and other viewmodels will trigger it and then MainWindowViewModel will switch to the needed view?

Why you need to switch from within one viewmodel to another? Is thecfact that mainviewmodel manages them is not ok? — Tigran

Random Dev Random Dev · Accepted Answer · 2011-08-27T07:44:16

the solution you describe is one possibility. One other I can think of is using some kind of Navigation-Service (static class or interface you pass to all your child-Viewmodels) that do this kind of work.

If your MainWindowViewModel creates all the others I would stick to the interface solution. You can for example let the MainWindowVM implement such a interface and inject it into all the child-vm on creation. This is much the same as your event-approach but instead of the childs-providing and the main having to subscribe you have the main give something ... IMHO the better approach.

How can I switch views between viewmodels?

2 Answers