what's wrong with my databinding?

Question

I've copied code from the blank panorama project and made some adjustments, but somewhere something ain't right.

I've got my textblock set up:

<TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding ElementName=CurrentPlaceNow, Path=Temperature}" />

My model looks like this:

public class CurrentPlaceNowModel : INotifyPropertyChanged
{
    #region PropertyChanged()
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (null != handler)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion

    private string _temperature;
    public string Temperature
    {
        get
        {
            return _temperature;
        }
        set
        {
            if (value != _temperature)
            {
                _temperature = value;
                NotifyPropertyChanged("Temperature");
            }
        }
    }
}

And defined defined in the MainViewModel():

public CurrentPlaceNowModel CurrentPlaceNow = new CurrentPlaceNowModel();

Finally I've added a modifier to a buttonclick:

App.ViewModel.CurrentPlaceNow.Temperature = "foo";

Now, why isn't anything showing up in the textbox?

Answer 1

Your Binding should navigate through the ViewModel. Binding to an ElementName tries to look at another object in the Visual Tree.

Change your Binding to this:

<TextBlock 
    Grid.Column="0" 
    Grid.Row="0" 
    Text="{Binding CurrentPlaceNow.Temperature}" />

Verify your ViewModel's property is formatted properly:

private CurrentPlaceNowModel _CurrentPlaceNow = new CurrentPlaceNowModel();
public CurrentPlaceNowModel CurrentPlaceNow
{
   get { return _CurrentPlaceNow; }
   set
   {
       _CurrentPlaceNow = value;
       NotifyPropertyChanged("CurrentPlaceNow");
   }
}

As long as your View's DataContext is your MainViewModel, you are good to go.