by Geert
22. December 2011 19:11
Recently, I needed to retrieve binding information on a dependency property in a behavior. In WPF, this is all possible (of course) via the BindingOperations.GetBindingExpression method. However, the developers of Silverlight must have thought that developers are only interested in binding expressions starting from a FrameworkElement. So, this means you cannot get binding expressions from the following types while they can have bindings:
- DependencyObject
- UIElement
- Behavior
- TriggerAction
- TriggerBase
And much more. For a complete list, see this list.
Anyway, I was pretty sad that the Silverlight team decided for me that I would never need to check the binding expression inside a behavior (which I needed in this case). Anyway, below is an extension method that allows you to get the binding expression of any dependency property:
1: /// <summary>
2: /// Gets the binding expression for the specified dependency property.
3: /// </summary>
4: /// <param name="dependencyObject">The dependency object.</param>
5: /// <param name="dependencyProperty">The dependency property.</param>
6: /// <returns>
7: /// The <see cref="BindingExpression"/> or <c>null</c> if the property is not bound.
8: // </returns>
9: /// <exception cref="ArgumentNullException">The <paramref name="dependencyObject"/> is <c>null</c>.</exception>
10: /// <exception cref="ArgumentNullException">The <paramref name="dependencyProperty"/> is <c>null</c>.</exception>
11: public static BindingExpression GetBindingExpression(this DependencyObject dependencyObject, DependencyProperty dependencyProperty)
12: {
13: Argument.IsNotNull("dependencyObject", dependencyObject);
14: Argument.IsNotNull("dependencyProperty", dependencyProperty);
15:
16: return (dependencyObject.ReadLocalValue(dependencyProperty) as BindingExpression);
17: }
Of course, this extension method is included in Catel.
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