将ListBox内部的控件绑定到ListBox的源以外的其他源

Question

I have a ListBox bound to a source which provides data to the text property of the controls inside. Now I'd like to bind Foreground property of my textboxes to a different source other than the one the main ListBox is bound to!

My listbox is bound to a ObservableCollection and I want my textblock Foreground property bound to textColor which is located in ViewModel

public SolidColorBrush textColor
{
    get { return new SolidColorBrush(Colors.Red); }
}

both are in ViewModel class. I tried using Foreground="{Binding textColor}" but it seems XAML doesn't see it at all, should I do anything in the page so that it can see it, or is it because the parent ( ListBox ) is using a different source?

Edit :

More details:

I have a DataContext.cs class which I have defined my tables in it. I have a ViewModel.cs class which I have these in it

public class CViewModel : INotifyPropertyChanged
{
    private CDataContext myDB;

    public CViewModel(string DBConnectionString)
    {
        myDB = new CDataContext(DBConnectionString);
    }

    private ObservableCollection<Groups> _allGroups;
    public ObservableCollection<Groups> AllGroups
    {
        get { return _allGroups; }
        set
        {
            _allGroups = value;
            NotifyPropertyChanged("AllGroups");
        }
    }

    public string textColor
    {
        get { return "Tomato"; }
    }
}

Then I have my XAML file MainPage.xaml :

....
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
    <ListBox Margin="0,8,0,0"  toolkit:TiltEffect.IsTiltEnabled="True" x:Name="list" ItemsSource="{Binding AllGroups}" HorizontalAlignment="Center"  BorderThickness="4">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Grid Background="Orange" Width="125" Height="125" Margin="6" Tap="Counterlist_OnTap">
                    <TextBlock Name="gname" Foreground="White" Text="{Binding Name}" VerticalAlignment="Center" HorizontalAlignment="Center" TextAlignment="Center" TextWrapping="Wrap"/>
                    <TextBlock Name="ccl" Margin="0,0,0,-5" Foreground="{Binding textColor}" Text="{Binding Count}" FontSize="26" VerticalAlignment="Bottom" HorizontalAlignment="Left" />
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>
....

I also set DataContext of my MainPage to ViewModel in code behind:

this.DataContext = App.ViewModel;

Answer 1

All you have to do is declare a static class (eg a singleton with per-instance access) and explicitly set the property binding to look in that class instead of the parent-bound model.

Bottom line: Just set the Source explicitly through a StaticResource .

Answer 2

The textColor property is part of the CViewModel , not the Groups object that is the datacontext within the ItemTemplate.

Within the ItemTemplate you can reach out to the parent ViewModel with the following Element binding:

<TextBlock Name="ccl" Margin="0,0,0,-5"
           Foreground="{Binding ElementName=ContentPanel, Path=DataContext.textColor}"
           Text="{Binding Count}" FontSize="26"
           VerticalAlignment="Bottom" HorizontalAlignment="Left" />