private static void OnItemHeightOrWidthPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            WrapPanel source = (WrapPanel)d;
            double    value  = (double)e.NewValue;

            // Ignore the change if requested
            if (source._ignorePropertyChange)
            {
                source._ignorePropertyChange = false;
                return;
            }

            // Validate the length (which must either be NaN or a positive,
            // finite number)
            if (!value.IsNaN() && ((value <= 0.0) || double.IsPositiveInfinity(value)))
            {
                // Reset the property to its original state before throwing
                source._ignorePropertyChange = true;
                source.SetValue(e.Property, (double)e.OldValue);

                string message = string.Format(
                    CultureInfo.InvariantCulture,
                    Microsoft.Phone.Controls.Toolkit.Properties.Resources.WrapPanel_OnItemHeightOrWidthPropertyChanged_InvalidValue,
                    value);
                throw new ArgumentException(message, "value");
            }

            // The length properties affect measuring.
            source.InvalidateMeasure();
        }
        private static void OnOrientationPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            WrapPanel   source = (WrapPanel)d;
            Orientation value  = (Orientation)e.NewValue;

            // Ignore the change if requested
            if (source._ignorePropertyChange)
            {
                source._ignorePropertyChange = false;
                return;
            }

            // Validate the Orientation
            if ((value != Orientation.Horizontal) &&
                (value != Orientation.Vertical))
            {
                // Reset the property to its original state before throwing
                source._ignorePropertyChange = true;
                source.SetValue(OrientationProperty, (Orientation)e.OldValue);

                string message = string.Format(
                    CultureInfo.InvariantCulture,
                    Microsoft.Phone.Controls.Toolkit.Properties.Resources.WrapPanel_OnOrientationPropertyChanged_InvalidValue,
                    value);
                throw new ArgumentException(message, "value");
            }

            // Orientation affects measuring.
            source.InvalidateMeasure();
        }