wpf - Get Effective DependencyProperty value on a DependencyObject

As discussed in my previous post, - wpf - Dependency Property Value Precedence, and the original article on  Dependency Property Value Precedence; There exists situation where the value of some DependencyProperty is determined by at runtime according to the list of precedence. e..g the background of a TextBlock in a ToolWindow is null, but because the ToolWindow has background property overriden, you ends up saying the TextBlock to have the background of the ToolWindow.

 

 

Below shows the method that return an effective value of DependencyProperty identified by the propertyName parameter.

 

    /// <summary>
    /// Get the effective property from the Dependency Property and the Metadata system
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="propertyName"></param>
    /// <param name="element"></param>
    /// <returns></returns>
    public static T GetEffectiveDependencyPropertyValue<T>(string propertyName, FrameworkElement element)
    {
      if (element == null) throw new ArgumentNullException("element");
      if (propertyName == null) throw new ArgumentNullException("propertyName");

      var visual = (DependencyObject)element;
      while (visual != null)
      {
        var propertyDescriptor = DependencyPropertyDescriptor.FromName(propertyName, visual.GetType(), visual.GetType(), true);
        var propertyValue = propertyDescriptor.GetValue(visual);
        if (propertyValue != null)
        {
          return (T)propertyValue;
        }
        visual = LogicalTreeHelper.GetParent(visual);
      }

      return default(T); 
    }

 

 

To use it, you just do 

 

FrameworkElement visua = ...
var background = GetEffectiveDependencyPropertyValue<Brush>("Background", visual);