Problem with Dependency Property - silverlight-4.0

Question

I am using a websites code for reference, but what I am trying to do is not working. The backing property never changes...I dont know if what I am expecting to happen is wrong..
public class QuestionTemplateSelector : UserControl
{
public DataTemplate TemplateString { get; set; }
public DataTemplate TemplateBoolean { get; set; }
public DataTemplate TemplateSingleMultipleChoice { get; set; }
public DataTemplate TemplateAnyMultipleChoice { get; set; }
/// <summary>
/// The <see cref="QuestionType" /> dependency property's name.
/// </summary>
public const string QuestionTypePropertyName = "QuestionType";
/// <summary>
/// Gets or sets the value of the <see cref="QuestionType" />
/// property. This is a dependency property.
/// </summary>
public string QuestionType
{
get
{
return (string)GetValue(QuestionTypeProperty);
}
set
{
SetValue(QuestionTypeProperty, value);
}
}
/// <summary>
/// Identifies the <see cref="QuestionType" /> dependency property.
/// </summary>
public static readonly DependencyProperty QuestionTypeProperty = DependencyProperty.Register(
QuestionTypePropertyName,
typeof(string),
typeof(QuestionTemplateSelector), new PropertyMetadata(QuestionTypeChangedCallBack));
private static void QuestionTypeChangedCallBack(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
Debug.WriteLine(string.Format("Old Value: {1}{0}New Value: {2}", " - ", e.OldValue, e.NewValue));
}
public QuestionTemplateSelector():base()
{
Loaded += new RoutedEventHandler(OnLoaded);
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
string questiontype = QuestionType;
Debug.WriteLine(sender);
if (questiontype == "Boolean")
{
Content = TemplateBoolean.LoadContent() as UIElement;
}
else if (questiontype == "Free Text")
{
Content = TemplateString.LoadContent() as UIElement;
}
else if (questiontype == "Single Multiple Choice")
{
Content = TemplateSingleMultipleChoice.LoadContent() as UIElement;
}
else if (questiontype == "Any Multiple Choice")
{
Content = TemplateAnyMultipleChoice.LoadContent() as UIElement;
}
else
{
Content = null;
}
}//onLoaded
}//QuestionTemplateSelector
I have a feeling it has to do with the onloaded. Where I really need code is in the Callback, but because its static I cant get access to the instance methods I need. How should I proceed? I can post more code if you need.
public QuestionTemplateSelector():base()
{
Loaded += new RoutedEventHandler(OnLoaded);
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
string questiontype = QuestionType;
Debug.WriteLine(sender);
if (questiontype == "Boolean")
{
Content = TemplateBoolean.LoadContent() as UIElement;
}
else if (questiontype == "Free Text")
{
Content = TemplateString.LoadContent() as UIElement;
}
else if (questiontype == "Single Multiple Choice")
{
Content = TemplateSingleMultipleChoice.LoadContent() as UIElement;
}
else if (questiontype == "Any Multiple Choice")
{
Content = TemplateAnyMultipleChoice.LoadContent() as UIElement;
}
else
{
Content = null;
}
}//onLoaded
I can verify that the code is actually changing in the callback, but the CLR property seems to never be updated.

Answer 1

This is how I got it working. But I am not sure this is absolutely correct.
public class QuestionTemplateSelector : UserControl
{
public DataTemplate TemplateString { get; set; }
public DataTemplate TemplateBoolean { get; set; }
public DataTemplate TemplateSingleMultipleChoice { get; set; }
public DataTemplate TemplateAnyMultipleChoice { get; set; }
/// <summary>
/// The <see cref="QuestionType" /> dependency property's name.
/// </summary>
public const string QuestionTypePropertyName = "QuestionType";
/// <summary>
/// Gets or sets the value of the <see cref="QuestionType" />
/// property. This is a dependency property.
/// </summary>
public Int64 QuestionType
{
get
{
return (Int64)GetValue(QuestionTypeProperty);
}
set
{
SetValue(QuestionTypeProperty, value);
}
}
/// <summary>
/// Identifies the <see cref="QuestionType" /> dependency property.
/// </summary>
public static readonly DependencyProperty QuestionTypeProperty;
private static void QuestionTypeChangedCallBack(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
((QuestionTemplateSelector)obj).QuestionType = (Int64)e.NewValue;
OnLoaded(obj, (Int64)e.NewValue);
}
static QuestionTemplateSelector()
{
QuestionTypeProperty = DependencyProperty.Register(
"QuestionType",
typeof(Int64),
typeof(QuestionTemplateSelector), new PropertyMetadata(QuestionTypeChangedCallBack));
//Loaded += new RoutedEventHandler(OnLoaded);
}
private static void OnLoaded(DependencyObject obj, Int64 e)
{
Int64 questiontype = e;
if (questiontype == 1)
{
Debug.WriteLine("Boolean");
((QuestionTemplateSelector)obj).Content = ((QuestionTemplateSelector)obj).TemplateBoolean.LoadContent() as UIElement;
}
else if (questiontype == 2)
{
Debug.WriteLine("FreeText");
((QuestionTemplateSelector)obj).Content = ((QuestionTemplateSelector)obj).TemplateString.LoadContent() as UIElement;
}
else if (questiontype == 3)
{
Debug.WriteLine("Single Multiple Choice");
((QuestionTemplateSelector)obj).Content = ((QuestionTemplateSelector)obj).TemplateSingleMultipleChoice.LoadContent() as UIElement;
}
else if (questiontype == 4)
{
Debug.WriteLine("Any Multiple Choice");
((QuestionTemplateSelector)obj).Content = ((QuestionTemplateSelector)obj).TemplateAnyMultipleChoice.LoadContent() as UIElement;
}
else
{
Debug.WriteLine("NONE");
((QuestionTemplateSelector)obj).Content = null;
}
}//onLoaded
}//QuestionTemplateSelector