Where does a page's datacontext get set?

[mobynet1]

I am thoroughly confused (ha!, even I admit it! ;-) I have an uno application that has about a dozen pages. I am using the TabBar as the navigation method. When the app kicks off, the MainPage has a data context set somehow. I know this because of items I am displaying are properly bound sourced from the view model. What confuses me is when I establish a DataContextChanged event handler and look at the new view for any page, MainPage included, the new data context is the shell view model. I see no references to any view models in the shell VM. I am using MVVM instead of C# Markup. When I tried out MVUX, I at least saw the BindingXXXViewModel so I knew where I could look for things in that circumstance. I simply cannot find the vm reference.

When the app starts up, the initial MainPage gets set and any values I am binding from the MainPageViewModel are properly displayed. I see the initial app being rendered properly, but I used the IsDefault:true on the route map entry for the main page. I am setting the TabBar's initial active tab by setting the selected index on the TabBar object, but this has an odd glitch. The page for this programmatically set first page is blank and only gets set if I navigate to another tab then return to the tab I wanted selected in the first place. But, when I do that, the values I am binding to this new page are getting set in the view model (confirmed via debug), but are not getting bound to any field that references it. Also, I have to navigate to and from the desired page several times to get it to display.

Is this a race condition of some sort, or is there something I have missed? I do not know what type of setup you may need to see so tell me what code would be helpful to you and I will provide it.

[nickrandolph]

Hi @mobynet1 if you're able to share a sample project that reproduces this behavior, that's probably the quickest way for us to help.

w.r.t the DataContext on MainPage, it will get initially set to ShellViewModel as it's inherited but it should subsequently be set to MainViewModel. There is work being done to address this in a future release (unoplatform/uno.extensions#2451)

[mobynet1]

@nickrandolph thanks for the reply.

[mobynet1]

I have found a solution to my issue... Thanks to all!