MVVM updating of view element

Question

I have an app following the MVVM scheme. Where I have multiple View and viewmodels. On my mainPage I have a textblock that I would like to update with information from chosen elements.

Upon starting the app I insert a value from the mainviewmodel to test the binding so everything works here. Where the code is as follows:

<TextBlock Text="{Binding colorOfElement}" Grid.Row="1"/>

Code in mainviewmodel

 private string _colorOfElement;
    public string colorOfElement
    { 
        get
        {
            return _colorOfElement;
        }
        set
        {
            _colorOfElement = value;

            NotifyPropertyChanged("colorOfElement");

        }
    }

......

colorOfElement = "Test";

This is displayed correctly. When a user then interacts with an element an event is fired inside the new viewmodel, in here I have a reference to the mainviewmodel so I can easily update the string colorOfElement.

private MainViewModel mv;
......
    public void MouseDown(ManipulationStartedEventArgs obj)
    {
        FrameworkElement MovingElement = (FrameworkElement)obj.OriginalSource;

        Canvas canvas = FindParentOfType<Canvas>(MovingGear);

        obj.ManipulationContainer = canvas;
        obj.Handled = true;

        testViewModel viewModel = (testViewModel)MovingElement.DataContext;

        mv.colorOfElement = viewModel.model.Color;
    }

when this function executes I am send into the mainviewmodel and NotifyPropertyChanged is fired. But on the Application.Page that shows the view I cannot see any update of the variable but in the code the variable changes. Any idea for this binding problem?

Answer As I had tested the datacontext and everything was working the problem was in my public class.

     public class MainViewModel : ViewModelBase

Here It should include the INotifyPropertyChanged interface to enable the feature. So the simple solution is to add this and get:

     public class MainViewModel : ViewModelBase, INotifyPropertyChanged

Then you are good to go :)

Answer 1

Ensure that:

• DataContext is set to the right instance of the MainViewModel
• the MainViewModel implements the INotifyPropertyChanged Interface