C#•16mo ago

❔ WPF Change Views

Im trying to switch views with MVVM pattern

49 Replies

SnitrxmOP•16mo ago

I created a NavigationStore to save the currentViewModel the problem is

public partial class MainViewModel : ViewModelBase
    {
        private readonly NavigationStore _navigationStore;

        public ViewModelBase CurrentViewModel => _navigationStore.CurrentViewModel;

        public MainViewModel(NavigationStore navigationStore)
        {
            _navigationStore = navigationStore;
        }

        public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }
    }

public partial class MainViewModel : ViewModelBase
    {
        private readonly NavigationStore _navigationStore;

        public ViewModelBase CurrentViewModel => _navigationStore.CurrentViewModel;

        public MainViewModel(NavigationStore navigationStore)
        {
            _navigationStore = navigationStore;
        }

        public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }
    }

Everything works fine until this part When the navigationStore calls the OnCurrentViewModelChanged() function The logs is right, shows the new view to be displayed but the function OnPropertyChanged does not make any change

SnitrxmOP•16mo ago

SnitrxmOP•16mo ago

Im binding this way

Pobiega•16mo ago

your code shown above doesnt include any OnPropertyChanged listeners nvm, hidden in the baseclass ofc

SnitrxmOP•16mo ago

public class ViewModelBase : ObservableObject
    { 
    }

public class ViewModelBase : ObservableObject
    { 
    }

my base class extend the mvvm toolkit that already have the listener for OnPropertyChanged

br4kejet•16mo ago

what about if you try binding directly to the _navigationStore's CurrentViewModel? you'd have to make it public obviously...

SnitrxmOP•16mo ago

what do you mean? ohh nevermind i got i think i cant do it, cuz my dataContext is set to the mainViewModel not to NavigationStore

br4kejet•16mo ago

public partial class MainViewModel : ViewModelBase
{
    public NavigationStore NavigationStore { get; }

    public MainViewModel(NavigationStore navigationStore)
    {
        NavigationStore = navigationStore;
    }
}

public partial class MainViewModel : ViewModelBase
{
    public NavigationStore NavigationStore { get; }

    public MainViewModel(NavigationStore navigationStore)
    {
        NavigationStore = navigationStore;
    }
}

and then

Pobiega•16mo ago

but mainViewModel has a navigation store in it.

br4kejet•16mo ago

{Binding NavigationStore.CurrentViewModel} If that doesn't work then try putting those data templates into the ContentControl's resources. Maybe it isn't finding them in your window for some reason?

SnitrxmOP•16mo ago

when i initialize its blank now

br4kejet•16mo ago

In your window put d:DataContext="{d:DesignInstance MainViewModel}" so that you can see any binding errors then you won't get those 3 dotted lines under some binding expressions ... unless the binding is invalid

SnitrxmOP•16mo ago

<Grid>
        <ContentControl Content="{Binding NavigationStore.CurrentViewModel}" />
    </Grid>

<Grid>
        <ContentControl Content="{Binding NavigationStore.CurrentViewModel}" />
    </Grid>

It works the same ways as before okk

br4kejet•16mo ago

Also try moving those data templates into the ContentControl's resources instead it might not be finding the windows' resources for some reason If that still doesn't work then maybe you aren't even setting the windows' data context somehow?

SnitrxmOP•16mo ago

sry, but i dont get it, what do u mean with ContentCOntrol's resources, im kinda new in wpf

br4kejet•16mo ago

In your window you have Window.Resources, and anything inside that, are resources that the window and any of its children have access too

SnitrxmOP•16mo ago

I do

br4kejet•16mo ago

But the ContentControl might not be able to access them for some reason, so replace the content control with

<ContentControl Content="{Binding NavigationStore.CurrentViewModel}">
  <ContentControl.Resources>
    ... data templates here
  </ContentControl.Resources>
</ContentControl>

<ContentControl Content="{Binding NavigationStore.CurrentViewModel}">
  <ContentControl.Resources>
    ... data templates here
  </ContentControl.Resources>
</ContentControl>

If that also doesn't work then i'm not sure based on the code you provided

SnitrxmOP•16mo ago

yeah doesnt work

br4kejet•16mo ago

Unless the DateTemplate types don't match up with the type that CurrentViewModel becomes that could also be a problem

SnitrxmOP•16mo ago

as my experience, i thinks its a update in main windows problem

public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }

public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }

as I said this functions is called when a ViewModel is changed but the new viewModels does not update in .xaml

public class NavigationStore
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                MainViewModel M = new(this);
                M.OnCurrentViewModelChanged();
            }
        }
    }

public class NavigationStore
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                MainViewModel M = new(this);
                M.OnCurrentViewModelChanged();
            }
        }
    }

this is my class NavigationStore

br4kejet•16mo ago

Try changing ContentControl to ContentPresenter

SnitrxmOP•16mo ago

I know that calling the function this way its bad I tried to do it with an event

br4kejet•16mo ago

I looked at one of my old projects and it uses ContentPresenter, but rarely ContentControl

SnitrxmOP•16mo ago

but does not work ok doesnt work why its soo difficult to switching between views using mvvm pattern?

br4kejet•16mo ago

In your xaml are you still binding to CurrentViewModel or to NavigationStore.CurrentViewModel?

SnitrxmOP•16mo ago

NavigationStore.CurrentViewModel

br4kejet•16mo ago

and you're using the MainViewModel code i provided?

SnitrxmOP•16mo ago

yes

public partial class MainViewModel : ViewModelBase
    {
        public NavigationStore NavigationStore { get; }

        public ViewModelBase CurrentViewModel => NavigationStore.CurrentViewModel;

        public MainViewModel(NavigationStore navigationStore)
        {
            NavigationStore = navigationStore;
        }

        public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }
    }

public partial class MainViewModel : ViewModelBase
    {
        public NavigationStore NavigationStore { get; }

        public ViewModelBase CurrentViewModel => NavigationStore.CurrentViewModel;

        public MainViewModel(NavigationStore navigationStore)
        {
            NavigationStore = navigationStore;
        }

        public void OnCurrentViewModelChanged()
        {
            System.Diagnostics.Debug.WriteLine(CurrentViewModel); //ViewModels.AccountViewModel
            OnPropertyChanged(nameof(CurrentViewModel));
        }
    }

br4kejet•16mo ago

It's not working because you're creating a new instance of your MainViewModel each time the CurrentViewModel changes

public class NavigationStore
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                OnPropertyChanged(nameof(CurrentViewModel));
            }
        }
    }

public class NavigationStore
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                OnPropertyChanged(nameof(CurrentViewModel));
            }
        }
    }

if you use that instead, then it should work as long as your windows' data context is set to an instance of MainViewModel

SnitrxmOP•16mo ago

does not work

public class NavigationStore : ViewModelBase
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                OnPropertyChanged(nameof(CurrentViewModel));
            }
        }
    }

public class NavigationStore : ViewModelBase
    {
        public event Action CurrentViewModelChanged;
        private ViewModelBase _currentViewModel;
        public ViewModelBase CurrentViewModel
        {
            get => _currentViewModel;
            set
            {
                _currentViewModel = value;
                OnPropertyChanged(nameof(CurrentViewModel));
            }
        }
    }

i also added the

ViewModelbase

ViewModelbase

br4kejet•16mo ago

Are you sure your windows' DataContext is set to an instance of MainViewModel?

SnitrxmOP•16mo ago

yeah

public partial class MainWindow : Window
    {
        NavigationStore navigationStore = new();

        public MainWindow()
        {
            InitializeComponent();
            navigationStore.CurrentViewModel = new HomeViewModel(navigationStore);
            DataContext = new MainViewModel(navigationStore);
        }
    }

public partial class MainWindow : Window
    {
        NavigationStore navigationStore = new();

        public MainWindow()
        {
            InitializeComponent();
            navigationStore.CurrentViewModel = new HomeViewModel(navigationStore);
            DataContext = new MainViewModel(navigationStore);
        }
    }

br4kejet•16mo ago

I dunno then... something must be wrong with your WPF install if binding doesn't work

SnitrxmOP•16mo ago

do you have tutorial i that i can follow?

br4kejet•16mo ago

not really...

SnitrxmOP•16mo ago

i tried a lot tutorials in yt nothin works

br4kejet•16mo ago

is your project on github?

SnitrxmOP•16mo ago

i can put it to you take a look

br4kejet•16mo ago

if you do that then i can look

SnitrxmOP•16mo ago

hold on a sec please

SnitrxmOP•16mo ago

https://github.com/Snitrxm/ATM-System-MVVM

GitHub

GitHub - Snitrxm/ATM-System-MVVM

Contribute to Snitrxm/ATM-System-MVVM development by creating an account on GitHub.

SnitrxmOP•16mo ago

here u go i'll appreciated a lot if you can take a look for me

br4kejet•16mo ago

In your HomeView and AccountView classes, remove the code where you're setting DataContext because the data context will already be set to HomeViewModel and AccountViewModel automaticall, because of how data templates work and then it should work after that

SnitrxmOP•16mo ago

yeah its works i dunno why

br4kejet•16mo ago

wpf is spooky

SnitrxmOP•16mo ago

thx a lot bro

br4kejet•16mo ago

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ WPF Change Views