public UIElement Step()
{
UIElement result = null;
if (collection != null)
{
UIElementCollection uiecollection = null;
int count = GetCount();
if (count < 0 || index >= count)
{
return(null);
}
if (count == 1 && index == 0)
{
index++;
return((UIElement)collection[0]);
}
if (direction == VisualTreeWalkerDirection.ZForward || direction == VisualTreeWalkerDirection.ZReverse)
{
uiecollection = (UIElementCollection)collection;
if (uiecollection.z_sorted.Count != count)
{
#if SANITY
printf("VisualTreeWalker: unexpectedly got an unsorted UIElementCollection\n");
#endif
uiecollection.ResortByZIndex();
}
}
switch (direction)
{
case VisualTreeWalkerDirection.ZForward:
result = (UIElement)uiecollection.z_sorted[index];
break;
case VisualTreeWalkerDirection.ZReverse:
result = (UIElement)uiecollection.z_sorted[count - (index + 1)];
break;
case VisualTreeWalkerDirection.Logical: {
result = (UIElement)collection[index];
break;
}
case VisualTreeWalkerDirection.LogicalReverse: {
result = (UIElement)collection[(count - (index + 1))];
break;
}
}
index++;
}
else
{
if (index == 0)
{
index++;
result = (UIElement)content;
}
else
{
result = null;
}
}
return(result);
}
