I am working with the classes in the System.Windows.Documents namespace, trying to write some generic code that will conditionally set the value of certain dependency properties, depending on whether these properties exist on a given class.

For example, the following method assigns an arbitrary value to the Padding property of the passed FrameworkContentElement:

void SetElementPadding(FrameworkContentElement element)
{
    element.SetValue(Block.PaddingProperty, new Thickness(155d));
}

However, not all concrete implementations of FrameworkContentElement have a Padding property (Paragraph does but Span does not) so I would expect the property assignment to succeed for types that implement this property and to be silently ignored for types that do not.

But it seems that the above property assignment succeeds for instances of all derivatives of FrameworkContentElement, regardless of whether they implement the Padding property. I make this assumption because I have always been able to read back the assigned value.

I assume there is some flaw in the way I am assigning property values. What should I do to ensure that a given dependency property assignment is ignored by classes that do not implement that property?

Many thanks for your advice.

Tim