Silverlight Visual Tree Walker

Constrained by Silverlight’s FindName method and inspired by a blog note by Jim Baltzell-Gauthier and my own implementation of tree walker for ASP.NET, I came up with a corresponding code snippet for Silverlight.

What you get is two extension methods, Find to search for a single child component and FindAll to search for all children matching specified predicate.

Note that this way you have a complete freedom of what you would like to find. Controls of specific name, specific type, anything – is just a matter of correct predicate.

public static class VisualTreeWalker
{
    public static FrameworkElement Find( 
        this DependencyObject Parent, 
        Predicate<FrameworkElement> Predicate )
    {
        if ( Parent is FrameworkElement )
            if ( Predicate( (FrameworkElement)Parent ) )
                return (FrameworkElement)Parent;

        foreach ( DependencyObject child in GetChildren( Parent ) )
        {
            try
            {
                FrameworkElement childElement = child as FrameworkElement;
                if ( childElement != null )
                    if ( Predicate( childElement ) )
                        return childElement;
            }
            catch { }
        }
        return null;
    }

    public static FrameworkElement[] FindAll( 
        this DependencyObject Parent, 
        Predicate<FrameworkElement> Predicate )
    {
        List<FrameworkElement> ret = new List<FrameworkElement>();
        
        FindAllHelper( Parent, Predicate, ret );

        return ret.ToArray();
    }

    private static void FindAllHelper( 
        DependencyObject Parent, 
        Predicate<FrameworkElement> Predicate, 
        List<FrameworkElement> results )
    {
        if ( Parent is FrameworkElement )
            if ( Predicate( (FrameworkElement)Parent ) )                    
                results.Add( (FrameworkElement)Parent );

        // rekursja
        foreach ( DependencyObject child in GetChildren( Parent ) )
        {
            FindAllHelper( child, Predicate, results );
        }
    }

    private static IEnumerable<DependencyObject> 
        GetChildren( DependencyObject Parent )
    {
        int childCount = VisualTreeHelper.GetChildrenCount( Parent );

        for ( int i = 0; i < childCount; i++ )
        {
            yield return VisualTreeHelper.GetChild( Parent, i );
        }
    }
}

As an example, suppose you have a complex Silverlight Grid, called TheGrid, and somewhere deeply inside it there are three ToggleButtons (that was an original case which motivated me to write the above snippet). Now I just iterate:

foreach ( ToggleButton toggleButton in
   TheGrid                                /* parent control */
      .FindAll( c => c is ToggleButton )  /* searching */
      .Select( f => f as ToggleButton ) ) /* projection - casting */
{
   /* now I got all my child controls I need */
}