Listbox binding in Silverlight - data-binding

Question

I have a listbox on silverlight page, the datacontext of the page is set to an instance -- TestQuestions, please see the code below. The listbox uses a DataTemplate and its ItemSource is 'Answers' which is a property of the page's DataContext, everything works fine until I try to bind to 'ShowAnswer', a property on the page's DataContext within the DataTemplate. No matter what I tried it won't pick the property's value.
Thank you all for your help.
Xaml:
<ListBox ItemsSource="{Binding Path=Answers, Mode=TwoWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<RadioButton IsChecked="{Binding Path=Correct, Mode=TwoWay}" >
<Grid>
<StackPanel Visibility="{Binding Path=ShowAnswer}">
<Rectangle Fill="Blue" Visibility="{Binding Path=Correct}" />
</StackPanel>
<TextBlock Text="{Binding Path=AnswerText, Mode=TwoWay}" TextWrapping="Wrap" />
</Grid>
</RadioButton>
</DataTemplate>
</ListBox.ItemTemplate>
C#:
public class Answer
{
private bool correct = false;
public bool Correct
{
get { return correct; }
set
{
correct = value;
NotifyPropertyChanged("Correct");
}
}
private string answerText = false;
public string AnswerText
{
get { return answerText; }
set
{
answerText = value;
NotifyPropertyChanged("AnswerText");
}
}
}
public class TestQuestions
{
private ObservableCollection<Answer> answers = new ObservableCollection<Answer>();
public ObservableCollection<Answer> Answers
{
get { return answers; }
set
{
if (answers != value)
{
answers = value;
NotifyPropertyChanged("Answers");
}
}
}
private bool showAnswer = false;
public bool ShowAnswer
{
get { return showAnswer; }
set
{
showAnswer = value;
NotifyPropertyChanged("ShowAnswer");
}
}
}

Answer 1

It looks to me like you're trying to bind the UIElement.Visibility to a boolean value. Change your 'ShowAnswer' property from a boolean to a Visibility property and you should be set.
private Visibility showAnswer = Visibility.Collapsed;
public Visibility ShowAnswer
{
get { return showAnswer; }
set
{
showAnswer = value;
NotifyPropertyChanged("ShowAnswer");
}
}
EDIT:
If you are trying to bind to a property on the DataContext of the parent control, you could do this:
Name your UserControl
Example:
<UserControl x:Class="MvvmLightProto.MainPage"
x:Name="mainProtoPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Height="700"
Width="1200">
In the above example, the UserControl has the name of "mainProtoPage", now in your XAML, you could do this:
<StackPanel Visibility="{Binding DataContext.ShowAnswer, ElementName=mainProtoPage}">